bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuronal molecular mimicry in immune‐mediated neurologic disease
Authors: Levin Michael C. , Krichavsky Marc , Berk Jeff , Foley Shanon , Rosenfeld Myrna , Dalmau Josep , Chang Greg , Posner Jerome B. , Jacobson Steven
Published: January 2005

Molecular mimicry is implicated in the pathogenesis of autoimmune diseases such as diabetes mellitus, rheumatoid arthritis, and multiple sclerosis (MS). Cellular and antibody‐mediated immune responses to shared viral‐host antigens have been associated with the development of disease in these patients. Patients infected with human T‐lymphotropic virus type I (HTLV‐I) develop HTLV‐I‐associated myelopathy/tropical spastic paraparesis (HAM/TSP), an immunemediated disorder of the central nervous system (CNS) that resembles some forms of MS. Damage to neuronal processes in the CNS of HAM/TSP patients is associated with an activated cellular and antibody‐mediated immune response. In this study, IgG isolated from HAM/TSP patients was immunoreactive with uninfected neurons and this reactivity was HTLV‐I specific. HAM/TSP IgG stained uninfected neurons in human CNS and cell lines but not nonneuronal cells. Neuronal western blots showed IgG reactivity with a single 33‐kd band in all HAM/TSP patients tested. By contrast, no neuron‐specific IgG reactivity could be demonstrated from HTLV‐I seronegative controls and, more important, from HTLV‐I seropositive, neurologically asymptomatic individuals. Both immunocytochemical staining and western blot reactivity were abolished by preincubating HAM/TSP IgG with HTLV‐I protein lysate but not by control proteins. Staining of CNS tissue by a monoclonal antibody to HTLV‐I tax (an immunodominant HTLV‐I antigen) mimicked HAM/TSP IgG immunoreactivity. There was no staining by control antibodies. Absorption of HAM/TSP IgG with recombinant HTLV‐I tax protein or preincubation of CNS tissue with the monoclonal antibody to HTLV‐I tax abrogated the immunocytochemical and western blot reactivity of HAM/TSP IgG. Furthermore, in situ human IgG localized to neurons in HAM/TSP brain but not in normal brain. These data indicate that HAM/TSP patients develop an antibody response that targets uninfected neurons, yet reactivity is blocked by HTLV‐I, suggesting viral‐specific autoimmune reactivity to the CNS, the damaged target organ in HAM/TSP.
Interictal cortical excitability in migraine: A study using transcranial magnetic stimulation of motor and visual cortices
Authors: Áfra Judit , Mascia Addolorata , Phy Pascale Gérard , de Noordhout Alain Maertens , Schoenen Jean
Published: January 2005

We performed transcranial magnetic stimulations of the motor and visual cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks. By using a 13‐cm circular coil placed over the vertex and recordings of the first dorsal interosseus muscle, we measured thresholds (at rest and during contraction), amplitudes of motor evoked potentials and cortical silent periods. Paired stimulations with short (1–20 msec) interstimulus intervals were performed to assess intracortical inhibition. The visual cortex was stimulated with the same coil placed over the occipital scalp (7 cm above the inion) and the prevalence and threshold of phosphene production was determined. In patients with migraine with aura, motor thresholds during isometric contraction were significantly higher, whereas the prevalence of stimulation‐induced phosphene production was lower compared with healthy controls. These changes were not correlated with attack frequency or disease duration. No differences were found between subject groups in thresholds at rest, motor evoked potential amplitudes, cortical silent periods, or response curves after paired stimuli. These results are in favor of cortical hypoexcitability rather than hyperexcitability in patients with migraine with aura between attacks.
Distinct pH homeostatic features in lymphoblasts from Alzheimer's disease patients
Authors: Ibarreta Dolores , Urcelay Elena , Parrilla Roberto , Ayuso Matilde S.
Published: January 2005

Epstein‐Barr–transformed lymphocytes from Alzheimer's disease patients showed the following distinct features in controlling the intracellular pH compared with cells from normal age‐matched controls: (1)The αIgM‐induced intracellular acidification was more pronounced in Alzheimer's disease than control cells and this effect appears to be associated with a loss of effectiveness of a Ca2+/ calmodulin‐dependent mechanism in controlling the activity of the Na+/H+ exchanger; and (2) the intracellular H+‐buffering capacity and the rate of proton efflux in response to an acid load were both decreased in Alzheimer's disease cells. It is concluded that the amplitude of the intracellular pH changes under acidloading conditions will always be greater in Alzheimer's disease than in control cells.
Deficient transport of dehydroascorbic acid in the glucose transporter protein syndrome
Authors: Klepper Jörg , Vera Juan Carlos , de Vivo Darryl C.
Published: January 2005

The glucose transporter protein syndrome (GTPS) is caused by defective transport of glucose across the blood–brain barrier via the glucose transporter GLUT1, resulting in hypoglycorrhachia, infantile seizures, and developmental delay. Recent reports indicated that GLUT1 is a multifunctional transporter. We investigated the transport of vitamin C in its oxidized form (dehydroascorbic acid) via GLUT1 into erythrocytes of 2 patients with GTPS. In both patients, uptake of oxidized vitamin C was 61% of the mothers' values. Our findings are consistent with recent observations that vitamin C is transported in its oxidized form via GLUT1. We speculate that impaired transport of this substrate and perhaps other substrates in GTPS might contribute to the pathophysiology of this condition.
Genetic association of two chromosome 14 genes (presenilin 1 and α1‐Antichymotrypsin) with Alzheimer's disease
Authors: Wang Xiaoyan , DeKosky Steven T. , Wisniewski Stephen , Aston Christopher E. , Kamboh M. Ilyas
Published: January 2005

We have investigated the association of two candidate genes on chromosome 14, presenilin 1 (PS1) and α1‐antichymotrypsin (ACT), with the risk of sporadic Alzheimer's disease (AD) by using 427 AD cases and 250 controls. The frequency of the ACT*A allele was significantly higher in cases than controls (0.550 vs 0.466). The stratification of the ACT data by PS1 genotypes showed that the risk associated with the ACT*A allele was confined to PS1*1 carriers only. The two‐site haplotype data for PS1 and ACT showed that the A1 haplotype, carrying the ACT*A and PS1*1 alleles, was more frequent in cases then controls (0.310 vs 0.251), whereas the frequency of the T2 haplotype, carrying the ACT*T and PS1*2 alleles, was lower in cases than controls (0.177 vs 0.237). These data indicate a possible synergistic effect of these two loci on the risk of AD.
Matrix metalloproteinases contribute to the blood—brain barrier disruption during bacterial meningitis
Authors: Paul Robert , Lorenzl Stefan , Koedel Uwe , Sporer Bernd , Vogel Ulrich , Frosch Matthias , Pfister Hans‐Walter
Published: January 2005

In this study, we investigated the involvement of matrix metalloproteinases (MMPs) in the pathophysiology of bacterial meningitis. By using an enzyme immunoassay, high concentrations of MMP‐9 were detected in the cerebrospinal fluid (CSF) of adult patients with bacterial meningitis but not in controls, and in patients with Guilain‐Barré syndrome. Moreover, we observed significantly elevated concentrations of the tissue inhibitor of metalloproteinase‐1 (TIMP‐1) in the CSF of patients with bacterial meningitis, compared with controls. In a rat model of meningococcal meningitis, intracisternal injection of heat‐killed meningococci caused a disruption of the blood–;brain barrier (BBB), and increase in intracranial pressure, and CSF pleocytosis paralleled by the occurrence of MMP‐9 activity in the CSF 6 hours after meningococcal challenge. The MMP inhibitor batimastat (BB‐94) significantly reduced the BBB disruption and the increase in intracranial pressure irrespective of the time of batmastat administration (15 minutes before and 3 hours after meningococcal challenge) but failed to significantly reduce CSF white blood cell counts. In conclusion, our results suggest that MMPs are involved in the alterations of BBB permeability during experimental meningococcal meningitis.
Dopa‐responsive dystonia: A clinical and molecular genetic study
Authors: Bandmann O. , Valente E. M. , Holmans P. , Surtees R. A. H. , Walters J. H. , Wevers R. A. , Marsden C. D. , Wood N. W.
Published: January 2005

We have studied the GTP‐cyclohydrolase 1 (GCH‐1) gene in 30 patients with the diagnosis of clinically definite (n = 20) or possible (n = 10) dopa‐responsive dystonia (DRD) as well as in a child with atypical phenylketonuria due to complete GCH‐1 deficiency. A large number of new heterozygote mutations (seven point mutations, two splice site mutations and one deletion) as well as a new homozygote mutations in the child with atypical phenylketonuria were detecte. In addition, two previously described mutations wer found in two other cases. We further extended our investigation of GCH‐1 to the 5′ and 3′ regulatory regions and report the first detection of point mutations in the 5′ untranslated region. Demethylation of CpG islands does not appear to be an important causative factor for the GCH‐1 mutations in DRD. In addition, we have extended the clinical phenotype of genetically proven DRD to focal dystonia, dystonia with relapsing and remitting course, and DRD with onset in the first week of life. None of our DRD patients without a mutation in GCH‐1 had the 3‐bp deletion recently detected in DYT1, the causative gene for idiopathic torsion dystonia with linkage to 9q34.
Mechanism of selective motor neuronal death after exposure of spinal cord to glutamate: Involvement of glutamate‐induced nitric oxide in motor neuron toxicity and nonmotor neuron protection
Authors: Urushitani Makoto , Shimohama Shun , Kihara Takeshi , Sawada Hideyuki , Akaike Akinori , Ibi Masakazu , Inoue Ryotaku , Kitamura Yoshihisa , Taniguchi Takashi , Kimura Jun
Published: January 2005

In this study, we analyzed the mechanism of selective motor neuronal death, a characteristic of amyotrophic lateral sclerosis, using embryonic rat spinal cord culture. When dissociated cultures were exposed to low‐level glutamate (Glu) coadministered with the Glu transporter inhibitor L‐trans‐pyrrolidine‐2,4‐decarboxylate (PDC) for 24 hours, motor neurons were selectively injured through N‐methyl‐D‐asparate (NMDA) and α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA)/kainate receptors. Nitric oxide synthase (NOS) inhibitors attenuated this toxicity, and long‐acting nitric oxide (NO) donors damaged motor neurons selectively. Nonmotor neurons survived after exposure to low‐dose Glu/PDC, but Glu‐induced toxicity was potentiated by coadministration of an NO‐dependent guanylyl cyclase inhibitor. In addition, 8‐bromo‐cyclic GMP, a soluble cyclic GMP analogue, rescued nonmotor neurons, but not motor neurons, exposed to high‐dose Glu/PDC. Twenty‐four hours' incubation with PDC elevated the number of neuronal NOS‐immunoreactive neurons by about twofold compared with controls, and a double‐staining, study, using the motor neuron marker SMI32, revealed that most of them were nonmotor neurons. These findings suggest that selective motor neuronal death caused by chornic low‐level exposure to Glu is mediated by the formation of NO in nonmotor neurons, which inversely protects nonmotor neurons through the guanylyl cyclase‐cyclic GMP casade. Induction of neuronal NOS in nonmotor neurons might enhance both the toxicity of motor neurons and the protection of nonmotor neurons, which could explain the pathology of amyotrophic lateral sclerosis.
Matrilineal inheritance of complex I dysfunction in a multigenerational Parkinson's disease family
Authors: Swerdlow Russell H. , Parks Janice K. , Davis John N. , Cassarino David S. , Trimmer Patricia A. , Currie Lillian J. , Dougherty John , Bridges W. Scott , Bennett James P. , Wooten G. Frederick , Parker W. Davis
Published: January 2005

Recent data suggesting complex I dysfunction in Parkinson's disease (PD) arises from mitochondrial DNA (mtDNA) mutation does not conclusively answer whether the responsible genetic lesion is inherited (primary) or somatic (secondary). To address this question, we identified a family in which multiple members over three generations are affected with PD through exclusively maternal lines. Cytoplasmic hybrids (cybrids) were created for 15 family members over two generations by trnsferring each individual's mtDNA to mtDNA‐depleted human neuroblastoma cells. Eight of the 15 cybrid lines contained mtDNA obtained from maternally descended family members and seven contained mtDNA from paternally descended family members. After 6 weeks of culture, cybrid cell lines were assayed for complex I activity and oxidative stress, and mitochondrial morphology was analyzed by electron microscopy. Compared with the cybrid lines containing mtDNA from paternal descendants, cybrid lines containing mtDNA from maternal descendants had lower complex I activity, increased reactive oxygen species production, increased radical scavenging enzyme activities, and more abnormal mitochondrial morphologic features. These findings were present in cybrid lines containing mtDNA from maternal descendants with PD as well as in currently asymptomatic young maternal descendants, and support a precedent for inherited mtDNA mutation in some persons with PD.
Remodeling of neuronal circuitries in human temporal lobe epilepsy: Increased expression of highly polysialylated neural cell adhesion molecule in the hippocampus and the entorhinal cortex
Authors: Mikkonen Mia , Soininen Hilkka , Kälviäinen Reetta , Tapiola Tero , Ylinen Aarne , Vapalahti Matti , Paljärvi Leo , Pitkänen Asla
Published: January 2005

Neuronal loss and axonal sprouting are the most typical histopathological findings in the hippocampus of patients with drug‐refractory temporal lobe epilepsy (TLE). It is under dispute, however, whether remodeling of neuronal circuits is a continuous process or whether it occurs only during epileptogenesis. Also, little is known about the plasticity outside of the hippocampus. We investigated the immunoreactivity of the highly polysialylated neural cell adhesion molecule (PSA‐NCAM) in the surgically removed hippocampus and the entorhinal cortex of patients with drug‐refractory TLE (n = 25) and autopsy controls (n = 7). Previous studies have shown that the expression of PSA‐NCAM is associated with the induction of synaptic plasticity, neurite outgrowth, neuronal migration, and events requiring remodeling or repair of tissue. In patients with TLE, the optical density (OD) of punctate PSA‐NCAM immunoreactivity was increased both in the inner and outer molecular layers of the dentate gyrus, compared with controls. The intensity of PSA‐NCAM immunoreactivity in the inner molecular layer correlated with the duration of epilepsy, severity of hippocampal neuronal loss, density of mossy fiber sprouting, and astrogliosis. In TLE patients with only mild neuronal loss in the hippocampus, the density of infragranular immunopositive neurons was increased twofold compared with controls, whereas in TLE patients with severe neuronal loss, the infragranular PSA‐NCAM–positive cells were not present. In the hilus, the somata and tortuous dendrites of some surviving neurons were intensely stained in TLE. PSA‐NCAM immunoreactivity was also increased in CA1 and in layer II of the rostral entorhinal cortex, where immunopositive neurons were surrounded by PSA‐NCAM‐positive fibers and puncta. Our data provide evidence that synaptic reorganization is an active process in human drug‐refractory TLE. Moreover, remodeling is not limited to the dentate gyrus, but also occurs in the CA1 subfield and the entorhinal cortex.
Reduction in HTLV‐I proviral load and spontaneous lymphoproliferation in HTLV‐I–associated myelopathy/tropical spastic paraparesis patients treated with humanized anti‐tac
Authors: Lehky Tanya J. , Levin Michael C. , Kubota Ryuji , Bamford Richard N. , Flerlage Alfred N. , Soldan Samantha S. , Leist Thomas P. , Xavier Andrew , White Jeffrey D. , Brown Margaret , Fleisher Thomas A. , Top Lois E. , Light Susan , McFarland Henry F. , Waldmann Thomas A. , Jacobson Steven
Published: January 2005

Human T‐lymphotropic virus type I (HTLV‐I)‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurological disease that results from an interaction of retroviral infection and immune activation. In this study, five doses (1 mg/kg) of humanized anti‐Tac antibody were administered to 9 HAM/TSP patients at weeks 0,2,6,10, and 14. Preliminary immunological studies on HAM/TSP patients treated with humanized anti‐Tac indicate that there is a selective down‐regulation of activated T cells and a decrease in the HTLV‐I viral load in peripheral blood lymphocytes, most likely through the selective removal of HTLV‐I–infected, activated CD4+ lymphocytes.
Increased circulating antiganglioside antibodies in primary and secondary progressive multiple sclerosis
Authors: Sadatipour B. Tayyebeh , Greer Judith M. , Pender Michael P.
Published: January 2005

Plasma samples from 70 patients with multiple sclerosis (MS), 41 patients with other neurological diseases (OND), and 38 healthy subjects were examined for antibodies against gangliosides GM1, GM3, GD1a, GD1b, and GD3 using enzyme‐linked immunosorbent assays. The percentages of subjects with increased anti‐GM3 responses were significantly higher in the primary progressive MS (56.3%) and secondary progressive MS (42.9%) groups than in the relapsing‐remitting MS (2.9%), healthy subject (2.6%), and OND (14.6%) groups. Elevated antiganglioside antibodies may be secondary to axonal damage or may be a cause of axonal damage and accumulating disability in progressive MS. In either case, they may serve as a marker of axonal damage in MS.
Conformational aspects of polypeptides. XVIII. Conformational studies of oligopeptides derived from L‐alanine
Authors: Goodman Murray , Langsam Michael , Rosen Ira G.
Published: December 2004

The conformations of oligopeptides derived from L‐alanine and co‐oligomers of L‐alanine with γ‐methyl‐L‐glutamate were studied in several solvents via optical rotation and far‐ultraviolet spectroscopy. Calculated values for optical rotation based on model compounds were compared with experimental values for the oligomers. In trifluoroacetic and dichloroacetic acids, the oligomers and co‐oligomers exhibit rotations in close agreement with predicted values based on model compounds. Thus, in these solvents only nonhelical conformations exist. In trifluoroethanol, the experimental points of molar rotation for the pentamer and larger oligomers no longer follow the predicted values. In addition, the benzyloxycarbonyl and acetyl cononamers show b0 values of about −150, which demonstrates the presence of stable helical forms for these peptides. We also examined the molar extinction coefficients of oligopeptides in the 190 mμ region and determined the values for nonhelical peptide groups. The molar extinction coefficients per amide bond for the benzyloxycarbonyl and acetyl cononamers show extensive hypo‐chromism, once again indicating the presence of stable helices for these compounds in trifluoroethanol.
Asymmetric selection in the copolymerization of N‐carboxy‐L‐ and D‐alanine anhydride
Authors: Tsuruta Teiji , Inoue Shohei , Matsuura Kazuo
Published: December 2004

The copolymerization of N‐carboxy‐L‐ and D‐alanine anhydride with methanol as initiator was carried out. The enantiomer excess in the starting monomer mixture is preferentially incorporated into polymer chains, demonstrating asymmetric selection during the D‐ and L‐copolymerization. The mechanism of asymmetric‐selective polymerization of α‐amino acid NCA is discussed in terms of the stereoregulation by molecular asymmetry of the growing polymer chain.
Far‐infrared spectra of N‐methylacetamide and related compounds and hydrogen‐bond force constants
Authors: Itoh Koichi , Shimanouchi Takehiko
Published: December 2004

Far‐infrared spectra of N‐methylacetamide and other monosubstituted amides were measured in the liquid state in the region from 250 to 60 cm.−1. Bands characteristic of the molecules with a peptide bond were found and assigned to the hydrogen‐bond vibration and the CN torsional vibration. Far‐infrared and Raman spectra of crystalline N‐methylacetamide were measured. The normal coordinate treatment for the low‐temperature modification of cystalline N‐methylacetamide was made. A reasonable set of force constants can explain all the spectra and their change due to the modification transition.
Circular dichroism of polynucleotides: A general method applied to dimers
Authors: Johnson W. C. , Tinoco I.
Published: December 2004

A method is described which relates the circular dichroism of a polymer to its conformation. The method takes into account near and accidental degeneracies and eliminates the artificial distinction between degenerate and nondegenerate systems. Comparison of this method with perturbation theory indicates that the errors inherent in nondegenerate perturbation theory tend to cancel when a circular dichroism spectrum is calculated. The method is applied to dinucleoside phosphates.
Une Méthode de Dosage des Isomères de Rotation des Dipeptides en Solution par Spectroscopie infrarouge
Authors: Avignon Michel , Van Huong Pham
Published: December 2004

An infrared spectroscopic method of quantitative analysis of dipeptides CH3CONHCHR1CONHR2 in solution is proposed. The application of the method to a series of dipeptides with different side chains shows that the amount of the “bent form” tends to become important when the side chain is large.
Conformation of poly‐L‐tyrosine in aqueous solution
Authors: Patrone Eligio , Conio Giuseppina , Brighetti Sergio
Published: December 2004

The conformational transition of poly‐L‐tyrosine in 0.1M KCl was investigated by ORD and infrared spectroscopy, potentiometric titration, and sedimentation velocity experiments. It is shown that the fully ordered conformer is obtained by slow titration of the random coil with 0.1N HCl at 25°C. The charge‐induced transition, at variance with other poly‐α‐amino acids, is completed in a narrow range of α. An aggregation process was detected both by potentiometric titration and sedimentation velocity. The polyamino acid aggregates around α = 0.7 at 25°C when the conformational transition is almost complete. Infrared spectra, in the region of the amide I band (1650 cm−1) showed that the transition is a random coil → antiparallel β one. Evidence exists that the form is of the intramolecular type. The foregoing interpretations of ORD and CD spectra in terms of the α‐helix conformation are discussed.
The temperature‐dependent swelling of elastin
Authors: Gosline John M.
Published: December 2004

It is suggested that the temperature‐dependent swelling behavior of water‐swollen elastin is due entirely to the interaction of the numerous nonpolar groups in the elastin protein wiht the aqueous swelling solvent (i.e., ahydrophobic interaction). Flory‐Rehner theory for network swelling was used to test this hypothesis. Calculated values for the solvent–polymer interaction parameter, χ1, derived from swelling data indicate that water is a very poor solvent for elastin at all temperatures over the range 0–70° C. Comparison of the calculated χ1 values with theoretical values for the free energy of interaction of nonpolar solutes and water strongly suggests that the swelling behavior of elastin can be attributed quantitatively to hydrophobic interactions. The implications of these results for the structure and elastic mechanism of elastin are discussed.
Conformational analysis of CCK‐B agonists using 1H‐nmr and restrained molecular dynamics: Comparison of biologically active Boc‐Trp‐(N‐Me)Nle‐Asp‐Phe‐NH2 and inactive Boc‐Trp‐(N‐Me)Phe‐Asp‐Phe‐NH2
Authors: Goudreau N. , Weng J. H. , Roques B. P.
Published: December 2004

The tetrapeptide Boc‐Trp‐(N‐Me)Nle‐Asp‐Phe‐NH2 is a potent CCK‐B agonist. Replacement in this analogue of the norleucine residue by a phenylalanine, to yield Boc‐Trp‐(N‐Me)Phe‐Asp‐Phe‐NH2, led to a 740‐fold decrease in affinity whereas the same decrease in affinity was not observed in their nonmethylated counterparts. In order to ascertain the conformational preferences of these two N‐methylated tetrapeptides, a study by two‐dimensional (2D) nmr spectroscopy and molecular modeling was undertaken. The solution conformation of the two peptides was examined by 1H‐nmr in a d6‐DMSO/H2O (80 : 20) mixture. A cis‐trans equilibrium, induced by N‐methylation, was observed for both analogues, and the proton spectra of the two retamers were fully characterized in each case. 1H‐1H distance constraints, derived from 2D nuclear Overhauser effect spectroscopy and rotating frame nuclear Overhauser effect spectroscopy experiments, were used as inputs for subsequent restrained molecular dynamics simulations. Comparisons of the nmr and molecular modeling data point toward distinct conformational preferences for these two peptides with an opposite spatial orientation of the Trp residue, and could explain the large difference in their biological activities. Furthermore, the tridimensional structure of Boc‐Trp‐(N‐Me)Nle‐Asp‐Phe‐NH2 could serve as a model for the design of nonpeptide CCK‐B agonists. © 1994 John Wiley & Sons, Inc.
Rheological properties and conformational states of β‐conglycinin gels at acidic pH
Authors: Nagano Takao , Mori Hiroyuki , Nishinari Katsuyoshi
Published: December 2004

The heat‐induced gelation of β‐conglycinin was investigated by dynamic viscoelastic measurements as a function of pH. At pH values below 5.5–6.0, the storage modulus G′ rapidly increased with decreasing pH. The conformational states of both sols and gels of β‐conglycinin were investigated by Fourier transform ir (FTIR) and by differential scanning calorimetry (DSC). The degree of protonation of the carboxyl groups of β‐conglycinin, when examined by FTIR indicated that, as would be expected, the degree of protonation increased with decreasing pH below pH 6.0. DSC measurements suggest that β‐conglycinin tends toward thermal denaturation with decreasing pH (below pH 6.0). Second‐derivative FTIR spectra for β‐conglycinin gels show that a band at 1620 cm−1 (associated with exposed β‐strands) develops with decreasing pH. The results suggest that β‐conglycinin undergoes denaturation with increasing protonation of its carboxyl groups, resulting in an increase in the amount of exposed β‐strands. The exposed β‐strands then intermolecularly bond to form gel networks. This process is promoted with decreasing pH, and as a result, rigid gels form at acidic pH values. © 1994 John Wiley & Sons, Inc.
Solution structure and dynamics of DNA topoisomers: Dynamic light scattering studies and Monte Carlo simulations
Authors: Langowski Jörg , Kapp Ulrike , Klenin Konstantin , Vologodskii Alexander
Published: December 2004

Using dynamic light scattering (DLS), we have measured the diffusion coefficient and internal motions of narrow topoisomer distributions of pUCl8 DNA (2687 base pairs) as a function of linking number. The topoisomer distributions were prepared by C‐18 reversed phase high performance liquid chromatography separation of topoisomerase I/ethidium‐generated topoisomer families. The measured diffusion coefficients agree well with those predicted by a Monte Carlo model for the generation of equilibrium ensembles of DNA topoisomers of defined linking number. The only parameters used in the model were the bending persistence length, torsional rigidity, and hydrodynamic radius of DNA known independently from other techniques. Two different values for the torsional rigidity, α = 4 · 10−12 and 8.8 · 10−12 dyn cm, were used. Intrachain interactions in the DNA were taken into account by using an “effective DNA radius,” which was varied between rDNA = 1–8 nm. The best agreement between the measured and calculated values was obtained for α = 4 · 10−12 dyn cm, rDNA = 4 nm. The internal motions of the DNA topoisomers were characterized by the amplitude of the fast relaxation of the DLS autocorrelation function. Our earlier result that supercoiling leads to a decrease in the amplitude of internal motion was confirmed. In addition, we see a characteristic maximum of the internal motion amplitude at a superhelix density of σ = −0.03. The maximum occurs in the same range as a structural transition in pUC8 dimers previously described by L. Song et al. (1990 J. Mol. Biol. 214, 307–326). © 1994 John Wiley & Sons, Inc.
β‐Alanine containing cyclic peptides with turned structure: The “pseudo type II β‐turn.” VI
Authors: Pavone Vincenzo , Lombardi Angelina , Saviano Michele , Nastri Flavia , Fattorusso Roberto , Maglio Ornella , Isernia Carla , Paolillo Livio , Pedone Carlo
Published: December 2004

In the present paper we describe the synthesis, purification, single crystal x‐ray analysis, and nmr solution characterization, combined with restrained molecular dynamic simulations, of the cyclic hexapeptide cyclo‐(L‐Pro‐L‐Phe‐β‐Ala)2. The peptide was synthesized by classical solution methods and the cyclization of the free hexapeptide was accomplished in good yields in diluted methylene chloride solution using N,N‐dicyclohexyl‐carbodiimide. The compound crystallizes in the monoclinic space group P21 from methanol‐dichloro‐methane solution. The two identical halves of the molecule adopt in the solid state two different conformations. One β‐Ala‐L‐Pro peptide bond is trans, while the second is cis. The molecule is present in dimethylsulfoxide d6 solutions as a mixture of conformational families. One of these corresponds to a C2 symmetrical molecule with both β‐Ala‐Pro cis peptide bonds, while the second major conformation is very similar to that observed in the solid state. All Pro‐Phe segments, both in the solid state and the symmetrical and unsym‐metrical solution conformations, display ϕ,ψ angles close to that of position i + 1 and i + 2 of type II β‐turns. In addition, the segments preceeded by a trans β‐Ala‐Pro peptide bond are characterized by a typical i ← i + 3 hydrogen bond, which is absent in the conformer containing a cis β‐Ala‐Pro peptide bond. The latter conformation corresponds to a new structural domain we define as the “pseudo type II β‐turn.” © 1994 John Wiley & Sons, Inc.
New characteristic signatures from time‐dependent static light scattering during polymer depolymerization, with application to proteoglycan subunit degradation
Authors: Ghosh Snehasish , Reed Wayne F.
Published: December 2004

Models were developed for the time‐dependent light scattering intensity for simply branched (“comb”) polymers undergoing one or more of three distinguishable degradation mechanisms: (a) stripping off the side chains, (b) randomly degrading off the side chains, and (c) randomly degrading the backbone. The model equations were applied to the analysis of different types of degradation of simply branched biopolymers—bovine nasal cartilage proteoglycan subunits (or “monomers”); NaOH stripped off the glycosaminoglycan (GAG) chains from the protein backbone [mechanism (a)], whereas hyaluronidase seemed to randomly cleave the GAG side chains [mechanism (b)], and HCl both stripped the GAG side chains and randomly cleaved the protein backbone [combined mechanisms (a) and (c)]. The reactions were followed with time‐dependent multiangle, static light scattering. The time‐resolved total scattering technique allowed degradation rate constants and percentage of material in the branched polymer backbone and side chains to be determined, in addition to the mechanisms involved. These new time‐dependent light scattering profiles are added to the growing library of functions from which deductions can be made concerning polymer structure and associated degradation mechanisms and kinetics. These conclusions, drawn from time‐dependent “batch” light scattering, are substantiated by preliminary size exclusion chromatography results and chemical binding assays for sulfated GAGs. © 1995 John Wiley & Sons, Inc.
Duplex to quadruplex equilibrium of the self‐complementary oligonucleotide d(GGGGCCCC)
Authors: Deng Hong , Braunlin William H.
Published: December 2004

The structure of the deoxyaligonucleotide d(GGGGCCCC) has been monitored by 1H and 31 P NMR, and by gel electrophoresis. In low‐salt solution, this oligonucleotide forms a stable duplex structure. Upon titration with KCl, an equilibrium is established between duplex and quadruplex forms. The quadruplex form is the dominant one at physiological KCl concentrations, despite the fact that fewer hydrogen bonds are formed per strand in the quadruplex than in the duplex. © 1995 John Wiley & Sons, Inc.
Density distribution of calcium‐induced alginate gels. A numerical study
Authors: Mikkelsen Arne , Elgsaeter Arnljot
Published: December 2004

Charged polysaccharides often form hydrogels in the presence of cations. In many applications the polymer network density distribution and associated physical properties are of major practical importance. Depending on the detailed conditions, the resulting gel density may vary from fully homogeneous to strongly inhomogeneous.

We have established a simple set of coupled chemical reaction–diffusion equations to model the gelling process of calcium‐induced alginate gels. The necessary algorithms for numerical solution of the resulting simultaneous parabolic differential equations have been developed both for one‐dimensional models and three‐ldimensional models with cylindrical or spherical symmetry. The algorithms make use of the Crank–Nicolson implicit finite difference method. The results of the numerical analyses of the gel formation can be divided into several different regimes depending on the physical and chemical parameters of the alginates and the cations. The numerical results are in good agreements with reported experimental results. © 1995 John Wiley & Sons, Inc.
Kinetics of protein folding: Nucleation mechanism, time scales, and pathways
Authors: Guo Zhuyan , Thirumalai D.
Published: December 2004

The kinetics and thermodynamics of protein folding is investigated using low friction Langevin simulation of minimal continuum mode of proteins. We show that the model protein has two characteristic temperatures: (a) Tθ, at which the chain undergoes a collapse transition from an extended conformation; (b) Tf(< Tθ), at which a finite size first‐order transition to the folded state takes place. The kinetics of approach to the native state from initially denatured conformations is probed by several novel correlation functions. We find that the overall kinetics of approach to the native conformation occurs via a three‐stage multiple pathway mechanism. The initial stage, characterized by a series of local dihedral angle transitions, eventually results in the compaction of the protein. Subsequently, the molecule acquires native‐like structures during the second stage of folding. The final stage of folding involves activated transitions from one of the native‐like structures to the native conformation. The first two stages are characterized by a multiplicity of pathways while relatively few paths are involved in the final stage. A detailed analysis of the dynamics of individual trajectories reveals a novel picture of protein folding. We find that afraction of the initial population reaches the native conformation without the formation of any detectable intermediates. This pathway is associated with a nucleation mechanism, i.e., once a critical number of tertiary contacts are established then the native state is reached rapidly. The remaining fraction of molecules become trapped in misfolded structures (stabilized by incorrect tertiary contacts). The slow folding involves transitions over barriers from these structures to the native conformation. The theoretical predictions are compared with recent experiments that probe protein folding kinetics by hydrogen exchange labeling technique. © 1995 John Wiley & Sons, Inc.
The development of potent peptide agonists and antagonists for the endothelin receptors
Authors: Cody Wayne L. , Doherty Annette M.
Published: December 2004

The endothelins (ETs), sarafotoxins (SRTXs), vasoactive intestinal contractor (VIC), and bibrotoxin are a family of potent vasoconstrictor peptides. All peptides in this family possess 21 amino acids arranged in a unique bicyclic motif formed between cystine bridges in the 1–15 and 3–11 positions. Since the discovery of endothelin‐1 (ET‐1) in 1988, significant effort has been focused on the understanding of its structure–activity relationships. The identification of endothelin receptor subtypes has led to the discovery/design of potent peptide agonists and antagonists, along with nonpeptide antagonists of endothelin with varying levels of potency and receptor subtype selectivity. In keeping with the theme of this journal, this review will focus only on the development of peptidic‐based agonists and antagonists of endothelin in addition to their applications in understanding the physiological and/or pathophysiological role of endothelin and its isopeptides. © 1994 John Wiley & Sons, Inc.
Structure–activity relationships of neuropeptide Y analogues with respect to Y1 and Y2 receptors
Authors: Beck‐Sickinger Annette G. , Jung Günther
Published: December 2004

Secondary structure investigations, affinities, and activities of neuropeptide Y analogues with respect to the Y1 and the Y2 receptor are reviewed. The results are discussed with respect to the different prerequisites for affinities to both receptor subtypes. The results from a systematic scanning of the hormone using L‐alanine and from a large variety of discontinuous and cyclic analogs suggest that two different conformations of neuropeptide Y are adopted at the Y1 and Y2 receptors. Whereas a C‐terminal turn structure is suggested for Y1 receptor affinity, an α‐helical conformation of the C‐terminus is afforded for good binding to the Y2 receptor. © 1994 John Wiley & Sons, Inc.
Enhancement of cheese flavors with microbial esterases
Authors: Huang H. T. , Dooley J. G.
Published: December 2004

The characteristic flavor of hard Italian cheeses is associated with the presence of fatty acids, particularly butyric acid, liberated from milk fat during the ripening process. To ensure proper development and control of flavor, animal pregastric esterases or lipases are routinely added to the milk before coagulation of the curd. Such esterases are also used to generate flavor in enzyme modified cheese and other dairy products.

Esterases from microbial sources have been investigated as agents to enhance flavor in cheese. We have found that an esterase from Mucor miehei exhibits the type of lipolytic activity needed for this application. Romano and fontina cheeses of excellent quality have been prepared by the use of this esterase. It has also been used successfully in the preparation of enzyme modified cheese, and, in turn, processed American cheese.
SCP production by Chaetomium cellulolyticum, a new thermotolerant cellulolytic fungus
Authors: Moo‐Young M. , Chahal D. S. , Swan J. E. , Robinson C. W.
Published: December 2004

Chaetomium cellulolyticum, a newly isolated cellulolytic fungus, showed 50–100% faster growth rates and over 80% more final biomass‐protein formation than Trichoderma viride, a well‐known high cellulase‐producing cellulolytic organism, when cultivated on Solka‐floc (a purified, predominantly amorphorous form of cellulose) or partially delignified sawdust (consisting of a mixture of hardwoods) as the sole‐carbon source in the fermentation media. However, in both cases, T. viride produced much higher quantities of free cellulases at faster rates and also degraded more substrate than C. cellulolyticum. It is concluded that the synthesis mechanisms and/or the nature of the cellulase complexes of the two types of organisms are quite different such that C. cellulolyticum is more optimal for single‐cell protein (SCP) production, while T. viride is more optimal for the production of extracellular cellulases.

It was also found that the amino acid composition of C. cellulolyticum is generally better than that of T. viride and compares favorably with those of the FAO reference protein, alfalfa, and soya meal. In addition, preliminary feeding trials on rats have shown no adverse effects of the SCP produced by C. cellulolyticum fermentations.
Effect of drop interactions on the performance of hydrocarbon fermentors
Authors: Bajpai R. K. , Ramkrishna D. , Prokop A.
Published: December 2004

A drop‐interaction model devised by the authors, which successfully predicts experimentally observed drop‐size distributions in stirred batch vessels, has been used to assess the importance of droplet coalescence and redispersion in hydrocarbon fermentation yields. Calculations, which have been made with both n‐alkane and gas–oil fermentations, have been compared with previous calculations based on simpler and, hence, less realistic droplet interaction mechanisms. The comparison shows that the differences in yield are not spectacularly different.
Pore dimensions for accumulating biomass. II. Microbes that form spores and exhibit mycelial growth
Authors: Messing R. A. , Oppermann R. A. , Kolot F. B.
Published: December 2004

The relationship between the dimensions of a spore and the accumulation of that microbe in a porous, inorganic structure has been determined. In order to achieve high accumulation of mycelial growth, at least 70% of the pores of an inorganic carrier should have pore diameters in the range of one times the smallest dimension of the fungal spore but less than about 16 times the largest dimension of that spore. This relationship was established by varying the physical parameters of the carriers as well as their chemical composition.
Studies on the mechanism of enzymatic hydrolysis of cellulosic substances
Authors: Ghose T. K. , Bisaria V. S.
Published: December 2004

Most cellulosic substances contain appreciable amounts of cellulose and hemicellulose, which on enzymatic hydrolysis mainly yield a mixture of glucose, cellobiose, and xylose. In this paper, studies on the mechanisms of hydrolysis of bagasse (a complex native cellulosic waste left after extraction of juice from can sugar) by the cellulase enzyme components are described in light of their adsorption characteristics. Simultaneous adsorption of exo‐ and endoglucanases on hydrolyzable cellulosics is the causative factor of the hydrolysis that follows immediately after. It supports the postulate of synergistic enzyme action proposed by Eriksson. Xylanase Pretreatment enhanced the hydrolysis of bagasse owing to the creation of more accessible cellulosic regions that are readily acted upon by exo‐ and endoglucanases. The synergistic action of the purified exoglucanase, endoglucanase, and xylanase has been found to be most effective for hydrolysis of bagasse but not for pure cellulose. Significant quantities of glucose are produced in β‐glucosidase‐free cellulase action on bagasse. Individual and combined action of the purified cellulase components on hydrolysis of native and delignified bagasse are discussed in respect to the release of sugars in the hydrolysate.
Production of microbial lipid: Effects of growth rate and oxygen on lipid synthesis and fatty acid composition of Rhodotorula gracilis
Authors: Choi S. Y. , Ryu Dewey D. Y. , Rhee J. S.
Published: December 2004

Microbial lipids produced by Rhodotorula gracilis NRRL Y‐1091 grown in continuous culture under nitrogen‐limiting condition were evaluated and the effects of growth rate and oxygen concentration on the degree of unsaturatoin of fatty acids studied. As the growth rate increased the protein content of the biomass increased but cell biomass, lipid content, and lipid productivity decreased; the specific lipid production rate remained constant at about 0.012 g lipid/g dry biomass/h. The maximum lipid content recorded was 49.8% (w/w) of the cell mass at a growth rate of 0.02 h−1. The growth rate also affected fatty acid composition; polyunsaturated fatty acids (C18:2 and C18:3) increaded with growth rate while other fatty acids (C16:0, C18:0, C18:1) decreased. Increase in oxygen concentration between 5 and 234μM increased the lipid content without significantly affecting its degree of unsaturation. On the other hand, the degree of unsaturation was significantly affected by specific oxygen uptake rate for this obligate aerobe, Rh. gracilis.
Continuous ethanol production from Jerusalem artichoke tubers. I. Use of free cells of Kluyveromyces marxianus
Authors: Margaritis Argyrios , Bajpai Pratima
Published: December 2004

The Continuous fermentation of Jerusalem artichoke juice to ethanol by free cells of Kluyveromyces marxianus UCD (FST) 55–82 has been studied in a continuous‐stirred‐tank bioreactor at 35°C and pH 4.6. A maximum yield of 90% of the theoretical was obtained at a dilution rate of 0.05 h−1. About 95% of the sugars were utilized at dilution rates lower than 0.15 h−1. Volumetric ethanol productivity and volumetric biomass productivity reached maximum values of 7 g ETOH/L/h and 0.6 g dry wt/L/h, respectively, at a dilution rate of 0.2 h−1. The maintenance energy coefficient for K. marxianus culture was found to be 0.46 g sugar/g biomass/h/ Oscillatory behavior was following a change in dilution rate from a previous steady state and from batch to continuous culture. Values of specific ethanol production rate and specific sugar uptake were found to increase almost linearly with the increase of the dilution rate. The maximum specific ethanol production rate and maximum specific sugar uptake rate were found to be 2.6 g ethanol/g/ cell/h and 7.9 sugars/g cell/h, respectively. Washout occurred at a dilution rate of 0.41 h−1.
Conversion of cheese whey to single‐cell protein
Authors: Sandhu D. K. , Waraich M. K.
Published: December 2004

Thirteen yeast species belonging to nine genera were screened for the production of single‐cell protein (SCP) using cheese whey as the substrate. Cheese whey supplemented with minerals and yeast extract proved to the best medium for yield, lactose utilization, biomass production, and conversion efficiency. Production of β‐galactosidase was studied in Brettanomyces anomalus, Kluyveromyces fragilis, Trichosporon cutaneum, and Wingea robertsii; the last proved to be the best strain combining high yield with shorter incubation period.
Calorimetric analysis of Escherichia coli in continuous culture
Authors: Ishikawa Yasufumi , Shoda Makoto
Published: December 2004

The heat evolution rate was measured in continuous culture of Escherichia coli k‐12 on glucose‐limiting medium. The specific heat production rate based on the dry cell mass increased in proportion to increase of dilution rate. The specific heat production rate based on a viable cell increased nonlinearly because the cell size varied in each dilution rate. Several thermochemical data were calculated for each dilution rate from the stoichiometric equation which was derived from elementary analysis of the cells. Growth yields based on energy measured directly was found to be less influenced by dilution rate than the growth yield based on consumed glucose. This suggested that the energy efficiency of utilization of catabolic energy for anabolism was almost constant.
Kinetics of the hydrolysis of lean meat protein by alcalase: Derivation of two alternative rate equations and their fit to experimental data
Authors: O'Meara G. M. , Munro P. A.
Published: December 2004

Two rate equations have been developed to model the hydrolysis of ground lean meat protein by Alcalase. The first equation was based on classical Michaelis‐Menten kinetics and the second on the adsorption of enzyme to the protein prior to reaction. It was assumed that this adsorption could be modelled by a Langmuir‐type adsorption isotherm. Each equation considered the enzyme to be competitively inhibited by reaction product, and considered enzyme inactivation to be first order. Both rate equations have been fitted to experimental data obtained from the hydrolysis of meat protein by Alcalase. Initial rate data indicated that the adsorption model was more appropriate. However, both equations gave satisfactory fits to 11 reaction progress curves determined over a wide range of enzyme and substrate concentrations.