bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and properties of isotactic polypropylene oriented by rolling with side constraints
Authors: Bartczak Z. , Morawiec J. , Galeski A.
Published: September 2002

The rolling of isotactic polypropylene (iPP) with a new method of rolling with side constraints (inside a channel) was studied. It was found that deformation processes by compression in a channel die and by rolling with side constraints proceed in very similar fashions (plane‐strain conditions) and result in materials of similar orientations and mechanical properties. The difference between the two processes is that rolling causes the destruction of the lamellar structure at a higher strain than compression. Dynamic mechanical measurements showed that rolling to a high strain produces not only a well‐developed orientation of the crystalline component but also high orientation and transverse ordering of the amorphous phase, leading to its transverse anisotropy. iPP deformed by rolling with side constraints has tensile properties similar to those of iPP deformed by other methods, such as conventional rolling or plane‐strain compression. The elastic modulus and ultimate strength measured along the rolling direction increase with an increasing deformation ratio. For samples deformed to a deformation ratio of 10.4, the ultimate strength reaches 340 MPa and can be further increased by postdeformation annealing. The oriented iPP also demonstrates extremely high impact toughness, especially in the direction of side constraints. Izod impact tests demonstrated that the material fracture on impact is very limited and that the impact strength exceeds 170 kJ/m2. In contrast to the tensile properties, there is an optimum deformation ratio around 5, for which the impact strength is the highest. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1413–1425, 2002
High‐strength uniaxially drawn tapes from scrap recycled poly(ethylene terephthalate)
Authors: Morawiec J. , Bartczak Z. , Pluta M. , Galeski A.
Published: September 2002

We made an effort to develop a manufacturing process for high‐strength packaging straps from recycled poly(ethylene terephthalate) (PET) beverage bottles. High‐strength tapes from low‐viscosity bottle‐grade PET cannot be obtained by single drawing to a natural draw ratio because the strength of such tapes is below expectation. To increase that strength, we developed a double‐drawing process, consisting of a second drawing step after free drawing with the natural draw ratio. The second stretching of tapes proceeded without necking and uniformly over the entire tape length. The extrusion/stretching was performed on the laboratory line, consisting of a single screw extruder, a chill roll, two sets of slow and fast rolls separated by a heating tunnel, and wind‐up roll. The tape drawn to a total draw ratio of 6 had a tensile strength slightly below 700 MPa and an initial slope of ≈ 15 GPa. Strain‐induced crystallization was the origin of strong texture after single drawing, whereas plastic deformation mechanisms of crystals were activated in the second step of drawing: the (100)[001] chain and (100)[010] transverse slips led to clear further refining of (1¯05) X‐ray pole figure. Industrial scale up of the double drawing delivered tapes with strength slightly below 700 MPa. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1426–1435, 2002
Remote hydrogen plasma chemical vapor deposition of silicon–carbon thin‐film materials from a hexamethyldisilane source: Characterization of the process and the deposits
Authors: Wróbel A. M. , Walkiewicz‐Pietrzykowska A. , Klemberg‐Sapieha J. E. , Hatanaka Y. , Aoki T. , Nakanishi Y.
Published: September 2002

Amorphous, hydrogenated silicon–carbon (a‐Si:C:H) films were produced by remote hydrogen plasma chemical vapor deposition (RHP‐CVD) with hexamethyldisilane (HMDS) as the starting compound. Microwave hydrogen plasma was the source of the atomic hydrogen active species. The susceptibility of particular bonds in the HMDS molecule toward the initiation step was established with tetramethylsilane as a model compound. The reaction mechanisms proposed for the RHP‐CVD process revealed the important role of polymerization in film growth. The temperature dependence of the film growth rate implied that the investigated RHP‐CVD was a nonthermally activated process. The a‐Si:C:H films produced at different deposition temperatures were characterized in terms of their chemical structure, surface and bulk composition, surface morphology, surface free energy, density, corrosion resistance, mechanical properties (adhesion and hardness), and optical properties (refractive index and optical band gap). The deposition temperature appeared to be a key parameter, precisely controlling the structure and properties of the resulting films. Based on the results of these studies, reasonable structure–property relationships were found. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1445–1458, 2002
Surface plasmon resonance of azobenzene‐incorporated polyelectrolyte thin films as an H+ indicator
Authors: Uznanski Pawel , Pecherz Janusz
Published: September 2002

An azo‐dye‐incorporated polyionene was spin‐coated as thin films on silver evaporated glass substrates. The films were used in conjunction with surface plasmon resonance (SPR) spectroscopy to examine the utility of combining these techniques for optical H+‐ion sensing. A method suggested by Kano and Kawata was used to enhance the sensitivity of the classical SPR measurements toward absorption detection. With the exposure of the composite polyionene films to HCl vapor, changes in the reflectivity signal were obtained in proportion to the concentration of H+ ions and according to the analyzing wavelength. The transformation of the parent azobenzene into the azohydrazone polar form determined the displacement of the absorption band and was the basis for the absorption‐enhanced SPR measurements. The difference in the SPR signals for the neutral sample and that exposed to interaction with HCl was most demonstrated for the wavelength at which the sample spectrum changed from being nonabsorbing to absorbing. The results show that chromophoric polyionenes are good materials for the production of sensitive substrates and can be combined with SPR spectroscopy for the optical sensing of aggressive gaseous species. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1459–1464, 2002
Oriented films from recycled poly(ethylene terephthalate)/recycled high‐density polyethylene compatibilized blends
Authors: Morawiec J. , Krasnikova N. P. , Galeski A. , Pracella M.
Published: September 2002

The process for the compatibilized blending of recycled poly(ethylene terephthalate) and recycled high‐density polyethylene with ethylene/glycidyl methacrylate copolymer was enlarged to the scale of a pilot plant. The addition of a compatibilizer effectively reduced the size of dispersed inclusions with better bonding to the matrix. The optimum contents of the compatibilizer were found to be around 4 pph. The extrusion and orientation of films from the blend were developed on an industrial scale, and the structure and properties of the obtained films were characterized. The crystalline phase of poly(ethylene terephthalate) in oriented films assumed a strong texture resulting from the plane‐strain state of the deformation of the films on the industrial machinery. The origin of the texture was mostly strain‐induced crystallization. The chain segments in the amorphous phase were oriented along the machine direction, but there was significant anisotropy of the chain packing in the amorphous phase in the plane perpendicular to the drawing direction, the pseudohexagonal packing of chain fragments being in register over the whole film. Such a texture of an oriented amorphous phase of poly(ethylene terephthalate) is reported here for the first time. The nonoriented and oriented films obtained with the industrial machinery showed good mechanical properties, with strengths up to 120 MPa and elongations to break of 40%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 02: 1486–1496, 2002
Anatomy of a successful K–12 educational outreach program in the health sciences: Eleven years experience at one medical sciences campus
Authors: Burns E. Robert
Published: September 2002

The Department of Anatomy and Neurobiology, College of Medicine, University of Arkansas for Medical Sciences (UAMS) is the administrative home of a nationally recognized educational outreach program in the health sciences for K–12 teachers (includes school nurses, counselors, etc.) and students. This program is called the Partners in Health Sciences (PIHS) program. It began in the summer of 1991 and is based on an annual needs assessment of the state's teachers. PIHS is a program available to all teachers and students in the state. It has several different components: (1) a cafeteria of 21 days of mini‐courses offered in the summer to meet the professional development needs of K–12 biology/health teachers and other school personnel; (2) weekly, interactive telecommunication broadcasts for students during the academic year; (3) intensive, 5‐day workshops that train five selected teachers at a time (10 per year) to use an authoring software program to develop grade‐appropriate interactive, computer‐assisted, instructional (CAI) modules for Internet (http://k14education.uams.edu) use by teachers and students; (4) a monthly science night for students and their parents at a local science magnet high school; (5) field trips to the UAMS campus for teachers and their students; (6) community‐requested presentations by program faculty; and (7) availability of earning undergraduate and graduate credit for science education majors in the College of Education, University of Arkansas at Little Rock. The data presented in this report span the period from 1991 through 2001. For all program activities, 14,084 different participants have consumed a total of 50,029 hours of education. Anat Rec (New Anat) 269:181–193, 2002. © 2002 Wiley‐Liss, Inc.
Infective agents in fixed human cadavers: A brief review and suggested guidelines
Authors: Demiryürek Deniz , Bayramoǧlu Alp , Ustaçelebi Şemsettin
Published: September 2002

Cadavers remain a principal teaching tool for anatomists and medical educators teaching gross anatomy. Infectious pathogens in cadavers that present particular risks include Mycobacterium tuberculosis, hepatitis B and C, the AIDS virus HIV, and prions that cause transmissible spongiform encephalopathies such as Creutzfeldt‐Jakob disease (CJD) and Gerstmann‐Straussler‐Scheinker syndrome (GSS). It is often claimed that fixatives are effective in inactivation of these agents. Unfortunately cadavers, even though they are fixed, may still pose infection hazards to those who handle them. Specific safety precautions are necessary to avoid accidental disease transmission from cadavers before and during dissection and to decontaminate the local environment afterward. In this brief review, we describe the infectious pathogens that can be detected in cadavers and suggest safety guidelines for the protection of all who handle cadavers against infectious hazards. Anat Rec (New Anat) 269:194–197, 2002. © 2002 Wiley‐Liss, Inc.
Adult onset acute myelogenous leukemia and electromagnetic fields in Los Angeles County: Bed‐heating and occupational exposures
Authors: Oppenheimer Mark , Preston‐Martin Susan
Published: September 2002

In a large matched population‐based case‐control study of acute myelogenous leukemia (AML), we did not find incident AML in Los Angeles County (1987–1994) to be associated with previous exposure to electric blankets, electrically heated waterbeds, or occupations with presumed high exposure to electromagnetic fields. Bioelectromagnetics 23:411–415, 2002. © 2002 Wiley‐Liss, Inc.
Current density threshold for the stimulation of neurons in the motor cortex area
Authors: Kowalski T. , Silny J. , Buchner H.
Published: September 2002

The aim of this study was to determine a current density threshold for exciting the motor cortex area of the brain. The current density threshold for excitation of nerve fibres (20 μm in diameter) found in the literature is approximately 1 A/m2at frequencies lower than 1 kHz. In consideration of a safety factor of 100, the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) recommends to restrict the exposure to 0.01 A/m2. The electromagnetic stimulation of neurons in the motor cortex is used in the clinical diagnosis of nerve lesions and neuropathy by means of magnetic or electrical transcranial stimulation. Combining medical data from clinical studies and technical specifications of the Magstim®Model 200 stimulator, we were able to compute the current density threshold for the excitation of the human motor cortex by means of the finite element method (FEM). A 3D‐CAD head model was built on the basis of magnetic resonance imaging (MRI) slices and segmented into four anatomical structures (scalp, skull, brain, and ventricular system) with different conductivities. A current density threshold for the stimulation of the motor cortex area of the upper limbs of 6 and 2.5 A/m2at 2.44 kHz and 50 Hz, respectively, was calculated. As these values lie above the recommended ICNIRP values by two orders of magnitude there is no need for lower safety standards with regard to stimulation of the brain. Bioelectromagnetics 23:421–428, 2002. © 2002 Wiley‐Liss, Inc.
Effect of ultraviolet B radiation and 100 Hz electromagnetic fields on proliferation and DNA synthesis of Jurkat cells
Authors: Nindl G. , Hughes E.F. , Johnson M.T. , Spandau D.F. , Vesper D.N. , Balcavage W.X.
Published: September 2002

The use of ultraviolet B light (UVB) has been proven to be highly effective for treatment of various inflammatory skin diseases, but UVB phototherapy is limited by its carcinogenic side effects. It is necessary to uncover effectors that augment UVB so that similar or improved efficacy can be obtained with lower UVB doses. We found that low frequency, low intensity electromagnetic fields (EMFs) can act as such an effector and synergistically inhibit T lymphocyte proliferation. We first characterized the effects of UVB on Jurkat cells, a model for cutaneous T lymphocytes, and determined UVB's dose dependent inhibition of cell proliferation and induction of apoptosis. Cells exposed to a sublethal UVB dose retained their sensitivity to UVB, but repetitive irradiation seemed to cause accumulation of delayed DNA damage. We then exposed cells to combinations of UVB plus EMFs and found that 100 Hz, 1 mT EMFs decrease DNA synthesis of UVB‐activated Jurkat cells by 34 ± 13% compared to UVB alone. The decrease is, however, most effective when relatively high UVB doses are employed. Since EMFs alone had only a very weak inhibitory effect (10 ± 2%), the data suggest that EMFs augment the cell killing effects of UVB in a synergistic way. These findings could provide the basis for development of new and improved clinical phototherapy protocols. Bioelectromagnetics 23:455–463, 2002. © 2002 Wiley‐Liss, Inc.
Developmental changes in Drosophila melanogaster following exposure to alternating electromagnetic fields
Authors: Mirabolghasemi Ghadire , Azarnia Mahnaz
Published: September 2002

This study investigated the biological effects of alternating electromagnetic fields (EMFs) on developmental stages of Drosophila melanogaster eggs and the first, second and third instar larvae stages. D. melanogaster eggs and larval stages were exposed to a 11 mT 50 Hz field produced by a pair of Helmholtz coils. Each stage was exposed to aEMFs for 2, 4, 6 and 8 h. Features of adult flies such as head, thorax, abdomen and other morphological changes were studied and compared. The frequency of abnormal flies was calculated using statistical methods at P < .05. The results obtained from exposing larvae in different stages of development showed a significant increase in the number of abnormal adult flies, whereas no significant increase was observed in the group arising from eggs exposed to aEMFs. Also, it appeared that duration of exposure correlates with the increase in the number of abnormal flies. There was no significant difference in mortality rate and sex distribution of the abnormal flies between field exposed and the control groups. Bioelectromagnetics 23:416–420, 2002. © 2002 Wiley‐Liss, Inc.
Quiet please, do not disturb: a hypothesis of embryo metabolism and viability
Authors: Leese Henry J.
Published: September 2002

This review uses nutritional markers of normal and impaired development to address the question; what makes a viable mammalian preimplantation embryo? Resolution of this question is important to ensure the long‐term safety of embryo‐based biotechnologies in man and domestic animals, the optimisation of embryo production and culture conditions and the development of methods to select viable embryos for replacement. After considering the nutrition of embryos and somatic cells, and the phenomenon of caloric restriction, it is concluded that preimplantation embryo survival is best served by a relatively low level of metabolism; a situation achieved by reducing the concentrations of nutrients in culture media and encouraging the use endogenous resources. BioEssays 24:845–849, 2002. © 2002 Wiley Periodicals, Inc.
Molecular control of neuronal migration
Authors: Park Hwan Tae , Wu Jane , Rao Yi
Published: September 2002

Our understanding of neuronal migration has been advanced by multidisciplinary approaches. At the cellular level, tangential and radial modes of neuronal migration contribute to different populations of neurons and have differential dependence on glial cells. At the molecular level, extracellular guidance cues have been identified and intracellular signal transduction pathways are beginning to be revealed. Interestingly, mechanisms guiding axon projection and neuronal migration appear to be conserved with those for chemotactic leukocytes. BioEssays 24:821–827, 2002. © 2002 Wiley Periodicals, Inc.
The modulator is a constitutive enhancer of a developmentally regulated sea urchin histone H2A gene
Authors: Spinelli Giovanni , Birnstiel Max L.
Published: September 2002

Going back to the late 1970s and early 1980s, we trace the Xenopus oocyte microinjection experiments that led to the emergence of the concept of “modulator”. The finding that the modulator could transactivate transcription from far upstream and in either orientation suggested that a new genetic element, different from the classical prokaryotic promoter sequences, had been discovered. This particular enhancer transactivates transcription of the sea urchin early (α) histone H2A gene which is regulated in early sea urchin development. We summarise the data from sea urchin microinjection experiments that confirm and extend the results obtained with Xenopus oocytes. We conclude that the H2A enhancer is bipartite, is located approx. 100 bp upstream of the TATAAATA box in the H2A gene of two sea urchin species and enhances transcription when placed at a position far upstream or far downstream of the gene unless an insulator intervenes between enhancer and promoter. Evidence from microinjection experiments with sea urchin embryos suggests that the developmental control of H2A expression resides not with the enhancer, which is constitutively active, but with a striking chromatin structure with two positioned nucleosomes near the 3′ end of the gene. Within this structure, there is an insulator element. BioEssays 24:850–857, 2002. © 2002 Wiley Periodicals, Inc.
Epithelial barrier function: assembly and structural features of the cornified cell envelope
Authors: Kalinin Andrey E. , Kajava Andrey V. , Steinert Peter M.
Published: September 2002

Terminally differentiating stratified squamous epithelial cells assemble a specialized protective barrier structure on their periphery termed the cornified cell envelope (CE). It is composed of numerous structural proteins that become cross‐linked by several transglutaminase enzymes into an insoluble macromolecular assembly. Several proteins are involved in the initial stages of CE assembly, but only certain proteins from a choice of more than 20 different proteins are used in the final stages of CE reinforcement, apparently to meet tissue‐specific requirements. In addition, a variable selection of proteins may be upregulated in response to genetic defects of one of the CE proteins or tissue injury, in an effort to maintain an effective barrier. Additionally, in the epidermis and hair fiber cuticle, a layer of lipids is covalently attached to the proteins, which provides essential water barrier properties. Here we describe our current understanding of CE structure, a possible mechanism of its assembly, and various disorders that cause a defective barrier. BioEssays 24:789–800, 2002. Published 2002 Wiley Periodicals, Inc.
Functional evolution of Hox proteins in arthropods
Authors: Vervoort Michel
Published: September 2002

It is presumed that the evolution of morphological diversity in animals and plants is driven by changes in the developmental processes that govern morphology, hence basically by changes in the function and/or expression of a defined set of genes that control these processes. A large body of evidence has suggested that changes in developmental gene regulation are the predominant mechanisms that sustain morphological evolution, being much more important than the evolution of the primary sequences and functions of proteins. Recent reports1, 2 challenge this idea by highlighting functional evolution of Hox proteins during the evolutionary history of arthropods. BioEssays 24:775–779, 2002. © 2002 Wiley Periodicals, Inc.
When machines get stuck—obstructed RNA polymerase II: displacement, degradation or suicide
Authors: van den Boom Vincent , Jaspers Nicolaas G.J. , Vermeulen Wim
Published: September 2002

The severe hereditary progeroid disorder Cockayne syndrome is a consequence of a defective transcription‐coupled repair (TCR) pathway. This special mode of DNA repair aids a RNA polymerase that is stalled by a DNA lesion in the template and ensures efficient DNA repair to permit resumption of transcription and prevent cell death. Although some key players in TCR, such as the Cockayne syndrome A (CSA) and B (CSB) proteins have been identified, the exact molecular mechanism still remains illusive. A recent report provides new unexpected insights into TCR in yeast.1 The identification and characterisation of a novel protein co‐purifying with the yeast homologue of CSB (Rad26) imposes reassessment of our current understanding of TCR in yeast. What about humans? BioEssays 24:780–784, 2002. © 2002 Wiley Periodicals, Inc.
Circular dichroism spectra of DNA quadruplexes [d(G5T5)]4 as formed with G4 and T4 tetrads and [d(G5T5) · d(A5C5)]2 as formed with Watson–Crick‐like (G‐C)2 and (T‐A)2 tetrads
Authors: Ito Hirotoshi , Tanaka Satoshi , Miyasaka Masaru
Published: September 2002

We utilize electrophoresis and find that a thermally treated equimolar mixture of the oligonucleotide d(G5T5) and its complementary oligonucleotide d(A5C5) exhibits either two bands or a single band in one lane, depending on the conditions of the incubation solutions. The thermally treated d(G5T5) solution loaded in a different lane exhibits a single band of the parallel quadruplex [d(G5T5)]4, which is composed of homocyclic hydrogen‐bonded G4 and T4 tetrads previously proposed. For the thermally treated equimolar mixture of d(G5T5) and d(A5C5), the fast band is assigned to a Watson–Crick d(G5T5) · d(A5C5) duplex, so that the slow band with the same low mobility as that of [d(G5T5)]4 may be assigned to either [d(G5T5)]4 itself or a [d(G5T5) · d(A5C5)]2 quadruplex. If the latter compound is true, this may be the antiparallel quadruplex composed of the heterocyclic hydrogen‐bonded G‐C‐G‐C and T‐A‐T‐A tetrads proposed previously. After removing these three bands for the duplex and two kinds of hypothetical quadruplexes, we electrophoretically elute the corresponding compounds in the same electrophoresis buffer using an electroeluter. The eluted compounds are ascertained to be stable by electrophoresis. The circular dichroism (CD) and UV absorption spectra measured for the three isolated compounds are found to be clearly different. For the electrophoretic elution of the hypothetical [d(G5T5)]4 quadruplex, the result of the molecularity of n = 4 obtained from the CD melting curve analysis provides further support for the formation of the parallel [d(G5T5)]4 quadruplex already proposed. For the thermally treated equimolar mixture of d(G5T5) and d(C5A5), the fast band with a molecularity of n = 2 corresponds to the Watson–Crick duplex, d(G5T5) · d(A5C5). The slow band with a molecularity of n = 4 indicates the antiparallel quadruplex [d(G5T5) · d(A5C5)]2, whose observed CD and UV spectra are different from those of [d(G5T5)]4. By electrophoresis, after reannealing the eluted compound [d(G5T5) · d(A5C5)]2, a distinct photograph showing the band splitting of this quadruplex band into the lower duplex and upper quadruplex bands is not possible; but by a transilluminator, we occasionally observe this band splitting with the naked eye. The linear response polarizability tensor calculations for the thus determined structures of the [d(G5T5)]4 quadruplex, the McGavin‐like [d(G5T5) · d(A5C5)]2 quadruplex, and the Watson–Crick d(G5T5) · d(A5C5) duplex are found to qualitatively predict the observed CD and UV spectra. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 61–80, 2002
Surface fluorescence resonance energy transfer studies on interfacial adsorption of Thermomyces (humicola) lanuginosa lipase, using monomolecular films of cis‐parinaric acid
Authors: Yapoudjian S. , Ivanova M. , Douchet I. , Zénatti A. , Sentis M. , Marine W. , Svendsen A. , Verger R.
Published: September 2002

The fluorescence resonance energy transfer (FRET) technique was adapted to study the process whereby lipase is adsorbed to monomolecular lipid films spread at the air–water interface. When cis‐parinaric acid (cis‐PnA) was spread over an aqueous subphase before the injection of sodium taurodeoxycholate (NaTDC) and Thermomyces lanuginosa lipase (TLL), no FRET was observed. Under these conditions, no adsorption of TLL was detected using an ELISA. In contrast, FRET occurred when cis‐PnA was spread over an aqueous subphase containing NaTDC and TLL. The FRET signals observed were attributed to the interactions between the adsorbed TLL and the cis‐PnA monomolecular films. Comparisons between the fluorescence emission spectra corresponding to the bulk phase and the aspirated film, in the presence and absence of TLL, showed that cis‐PnA was undetectable in the bulk phase. We concluded that the FRET originated from the interface and not from the bulk phase. Using surface FRET, we estimated that the surface excess of the catalytically inactive mutant, TLL(S146A), was 1.6 higher than that present in the wild‐type TLL. This finding is in agreement with independent measurements of the surface excess of TLL and TLL(S146A) on monomolecular films of cis‐PnA. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 121–128, 2002
Spectroscopic studies and PM5 semiempirical calculations of new Schiff bases of gossypol with polyoxaalkylamines
Authors: Przybylski Piotr , Bartl Franz , Brzezinski Bogumil
Published: September 2002

Three Schiff bases of racemic gossypol with polyoxaalkylamines were synthesized and studied by FTIR and 1H‐NMR spectroscopy, and their structures were calculated by the PM5 semiempirical method. These Schiff bases exist in the solid state and in solutions as enamine forms. An increasing length of the polyoxaalkyl chain causes the increase of the interaction of the oxygen atoms of this chain with the OH groups in the 6,6′ positions. This interaction is very well evidenced in the FTIR and 1H‐NMR spectra. The structures of the Schiff bases and the hydrogen bonds within these structures are discussed. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 111–120, 2002
Fourier transform IR and Fourier transform Raman spectroscopy studies of metallothionein‐III: Amide I band assignments and secondary structural comparison with metallothioneins‐I and ‐II
Authors: Shi Yan‐Bo , Fang Jiang‐Lin , Liu Xiao‐Yu , Du Liang , Tang Wen‐Xia
Published: September 2002

The secondary structures of porcine brain Cu4Zn3‐metallothionein (MT)‐III and Cd5Zn2MT‐I, Cd5Zn2MT‐II, and Zn7MT‐I from rabbit livers in the solid state are investigated by Fourier transform IR spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT‐Raman). The Cu4Zn3MT‐III contains 26–28% β‐turns and half‐turns, 13–14% 310‐helices, 47–49% random coils, and 11–12% β‐extended chains. The structural comparison of porcine brain Cu4Zn3MT‐III with rabbit liver Cd5Zn2MT‐I (II) and Zn7MT‐I shows that the contents of the random coil structure are obviously increased. The results indicate that the insert of an acidic hexapeptide in the α domain of Cu4Zn3MT‐III possibly forms an α helix. However, because the bands assigned to the α‐helix and random coil structures are overlapped in the spectra, the content of random coil structures in Cu4Zn3MT‐III is therefore higher than those in Cd5Zn2MT‐I, Cd5Zn2MT‐II, and Zn7MT‐I. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 81–88, 2002
Study of wheat high molecular weight 1Dx5 subunit by 13C and 1H solid‐state NMR. II. Roles of nonrepetitive terminal domains and length of repetitive domain
Authors: Alberti Enrica , Gilbert Simon M. , Tatham Arthur S. , Shewry Peter R. , Naito Akira , Okuda Kanna , Saitô Hazime , Gil Ana M.
Published: September 2002

This work follows a previous article that addressed the role of disulfide bonds in the behavior of the 1Dx5 subunit upon hydration. Here the roles of nonrepetitive terminal domains present and the length of the central repetitive domain in the hydration of 1Dx5 are investigated. This was achieved by comparing the hydration behavior of suitable model samples determined by 13C‐ and 1H‐NMR: an alkylated 1Dx5 subunit (alk1Dx5), a recombinant 58‐kDa peptide corresponding to the central repetitive domain of 1Dx5 (i.e., lacking the terminal domains), and two synthetic peptides (with 6 and 21 amino acid residues) based on the consensus repeat motifs of the central domain. The 13C cross‐polarization and magic angle spinning (MAS) experiments recorded as a function of hydration gave information about the protein or peptide fractions resisting plasticization. Conversely, 13C single pulse excitation and 1H‐MAS gave information on the more plasticized segments. The results are consistent with the previous proposal of a hydrated network held by hydrogen‐bonded glutamines and possibly hydrophobic interactions. The nonrepetitive terminal domains were found to induce water insolubility and a generally higher network hindrance. Shorter chain lengths were shown to increase plasticization and water solubility. However, at low water contents, the 21‐mer peptide was characterized by higher hindrance in the megahertz and kilohertz frequency ranges compared to the longer peptide; and a tendency for a few hydrogen‐bonded glutamines and hydrophobic residues to remain relatively hindered was still observed, as for the protein and large peptide. It is suggested that this ability is strongly dependent on the peptide primary structure. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 158–168, 2002
High‐throughput screening and quantitative structure‐efficacy relationship models of potential displacer molecules for ion‐exchange systems
Authors: Mazza Cecilia B. , Rege Kaushal , Breneman Curt M. , Sukumar N. , Dordick Jonathan S. , Cramer Steven M.
Published: September 2002

A technique is presented for the high‐throughput screening of ion‐exchange displacers. Potential displacers were employed to displace proteins in parallel batch ion‐exchange experiments. The percentage of protein displaced from a particular stationary phase was then used as a parameter to rank the displacers. By employing this technique, a large number of molecules possessing a range of affinities and properties could be rapidly evaluated. This data was then used together with traditional and electron density‐based transferable atom equivalent (TAE) molecular descriptors computed for the displacer molecules to produce quantitative structure‐efficacy relationship (QSER) models using a genetic algorithm/partial least squares (GA/PLS) regression approach. The QSER models were generated using a portion of the protein‐displacement data, with the remainder serving as a test set. Descriptor selection and model building was accomplished using a genetic algorithm/partial least squares approach. The resulting models were found to have high‐correlation coefficients and could be used to accurately predict the behavior of molecules not included in the training set. In addition, the models were employed to examine a virtual library of displacers based on modifications of neomycin to provide further insight into displacer design. The results presented here indicate that it may be possible to design displacers that can dramatically improve the effective selectivity of ion‐exchange chromatographic materials. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 60–72, 2002.
The use of microscale processing technologies for quantification of biocatalytic Baeyer‐Villiger oxidation kinetics
Authors: Doig Steven D. , Pickering Samuel C. R. , Lye Gary J. , Woodley John M.
Published: September 2002

Microscale processing techniques would be a useful tool for the rapid and efficient collection of biotransformation kinetic data as a basis for bioprocess design. Automated liquid handling systems can reduce labor intensity while the small scale reduces the demand for scarce materials such as substrate, product, and biocatalyst. Here we illustrate this concept by establishing the use of several microwell formats (96‐round, 96‐deep square and 24‐round well microtiter plates) for quantification of the kinetics of the E. coli TOP10 [pQR239] resting cell catalyzed Baeyer‐Villiger oxidation of bicyclo[3.2.0]hept‐2en‐6‐one using glycerol as a source of reducing power. By increasing the biocatalyst concentration until the biotransformation rate was oxygen mass‐transfer limited we can ensure that kinetic data collected are in the region away from oxygen limitation. Using a 96‐round well plate the effect of substrate (bicyclo[3.2.0]hept‐2en‐6‐one) concentration on the volumetric CHMO activity was examined and compared to data collected from 1.5‐L stirred‐tank experiments. The phenomenon and magnitude of substrate inhibition, observed at the larger scale, was accurately reproduced in the microwell format. We have used this as an illustrative example to demonstrate that under adequately defined conditions, automated microscale processing technologies can be used for the collection of quantitative kinetic data. Additionally, by using the experimentally determined stoichiometry for product formation and glycerol oxidation, we have estimated the maximum oxygen transfer rates as a function of well geometry and agitation rate. Oxygen‐transfer rates with an upper limit of between 33 mmol · L−1 · h−1 (based solely on product formation) and 390 mmol · L−1 · h−1 (based on product formation and glycerol oxidation) were achieved using a 96‐square well format plate shaken at 1300 rpm operated with a static surface area to volume ratio of 320 m2 · m−3. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 42–49, 2002.
Production of D‐amino acid oxidase (DAO) of Trigonopsis variabilis in Schizosaccharomyces pombe and the characterization of biocatalysts prepared with recombinant cells
Authors: Isoai Atsushi , Kimura Hidetoshi , Reichert Arno , Schörgendorfer Kurt , Nikaido Kiyokazu , Tohda Hideki , Giga‐Hama Yuko , Mutoh Norihiro , Kumagai Hiromichi
Published: September 2002

The cDNA of D‐amino acid oxidase (DAO) gene isolated from Trigonopsis variabilis was expressed in Schizosaccharomyces pombe. A clone, ASP327‐10, transformed with plasmid vector, pTL2M5DAO, expressed catalytically active DAO in the presence of G418, and converted Cephalosprin C to α‐ketoadipyl‐7‐cephalosporanic acid (KA‐7‐ACA) and glutaryl‐7‐aminocephalosporanic acid (GL‐7‐ACA). Biocatalysts were prepared using ASP327‐10 and T. variabilis, and evaluated to demonstrate the feasibility of recombinant S. pombe for industrial application. The cells were immobilized by crosslinking polyethylene imine after glutardialdehyde (GDA) fixation and permeabilization by alkaline treatment. Although the biocatalyst prepared from ASP327‐10 exhibited DAO activity, catalase activity still remained fully even after permeabilization, under which condition, the catalase activity of T. variabilis decreased to 20–30%. Heat treatment was required before cell fixation by GDA to inactivate the catalase in S. pombe. This improved the efficiency of bioconversion to GL‐7‐ACA, but caused poor mechanical strength in the biocatalyst of S. pombe. To overcome this weakness, a catalase‐deficient host strain was obtained by ethylmethansulfate mutagenesis. Moreover, taking economics into consideration, the integrative vector, pTL2M5DAO‐8XL, with multi‐copies of expression cassette was constructed to express DAO in S. pombe even in the absence of G418. The newly established integrant, ASP417‐7, did not exhibit any catalase activity so that heat treatment was not required. The obtained integrant and its biocatalyst were significantly improved in GL‐7ACA conversion ability and mechanical strength. This study demonstrates that the established integrant is a potential candidate as an alternative source of DAO enzyme. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 22–32, 2002.
Pilot‐scale production of (S)‐styrene oxide from styrene by recombinant Escherichia coli synthesizing styrene monooxygenase
Authors: Panke Sven , Held Martin , Wubbolts Marcel G. , Witholt Bernard , Schmid Andreas
Published: September 2002

Recombinant Escherichia coli JM101(pSPZ10) cells produce the styrene monooxygenase of Pseudomonas sp. strain VLB120, which catalyzes the oxidation of styrene to (S)‐styrene oxide at an enantiomeric excess larger than 99%. This biocatalyst was used to produce 388 g of styrene oxide in a two‐liquid phase 30‐L fed‐batch bioconversion. The average overall volumetric activity was 170 U per liter over a period of more than 10 h, equivalent to mass transfer rates of 10.2 mmoles per liter per hour at a phase ratio of 0.5. At this transfer rate, the biotransformation system appeared to be substrate mass‐transfer limited. The reactor had an estimated power input in the order of 5 W · L−1, which is close to values typically obtained with commercially operating units. The product could be easily purified by fractional distillation to a purity in excess of 97%. The process illustrates the feasibility of recombinant whole cell biotransformations in two‐liquid phase systems with toxic substrates and products. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 33–41, 2002.
Development of a novel diffusion‐based method to estimate the size of the aggregated Aβ species responsible for neurotoxicity
Authors: Wang Steven S.‐S. , Becerra‐Arteaga Alejandro , Good Theresa A.
Published: September 2002

β‐Amyloid peptide (Aβ) is the primary protein component of senile plaques in Alzheimer's disease and is believed to be responsible for the neurodegeneration associated with the disease. Aβ is toxic only when aggregated, however, the size and structure of the aggregated species associated with toxicity is unknown. In the present study, we developed a diffusion‐based method to simultaneously separate and detect the biological activity of toxic Aβ oligomers and used the method to examine the relationship between size of aggregated protein and toxicity to SH‐SY5Y cells. From these measurements, the effective diffusivity and hydrodynamic radius of the toxic oligomeric species of Aβ could be determined. A sensitivity analysis was performed to examine the effects of model assumptions used in data analysis on the effective diffusivity calculated. The method provides a new estimate of the size of small toxic Aβ species associated with fibril formation. This work contributes to our understanding of the relationship between Aβ structure and toxicity and with further refinements may aid in our ability to design agents which alter the Aβ aggregation/dissociation processes associated with neurotoxicity. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 50–59, 2002.
Integrated reactor concepts for the enzymatic kinetic synthesis of cephalexin
Authors: Schroën C. G. P. H. , Nierstrasz V. A. , Bosma R. , Kroon P. J. , Tjeerdsma P. S. , DeVroom E. , VanderLaan J. M. , Moody H. M. , Beeftink H. H. , Janssen A. E. M. , Tramper J.
Published: September 2002

Integrated process concepts for enzymatic cephalexin synthesis were investigated by our group, and this article focuses on the integration of reactions and product removal during the reactions. The last step in cephalexin production is the enzymatic kinetic coupling of activated phenylglycine (phenylglycine amide or phenylglycine methyl ester) and 7‐aminodeacetoxycephalosporanic acid (7‐ADCA). The traditional production of 7‐ADCA takes place via a chemical ring expansion step and an enzymatic hydrolysis step starting from penicillin G. However, 7‐ADCA can also be produced by the enzymatic hydrolysis of adipyl‐7‐ADCA. In this work, this reaction was combined with the enzymatic synthesis reaction and performed simultaneously (i.e., one‐pot synthesis). Furthermore, in situ product removal by adsorption and complexation were investigated as means of preventing enzymatic hydrolysis of cephalexin. We found that adipyl‐7‐ADCA hydrolysis and cephalexin synthesis could be performed simultaneously. The maximum yield on conversion (reaction) of the combined process was very similar to the yield of the separate processes performed under the same reaction conditions with the enzyme concentrations adjusted correctly. This implied that the number of reaction steps in the cephalexin process could be reduced significantly. The removal of cephalexin by adsorption was not specific enough to be applied in situ. The adsorbents also bound the substrates and therewith caused lower yields. Complexation with β‐naphthol proved to be an effective removal technique; however, it also showed a drawback in that the activity of the cephalexin‐synthesizing enzyme was influenced negatively. Complexation with β‐naphthol rendered a 50% higher cephalexin yield and considerably less byproduct formation (reduction of 40%) as compared to cephalexin synthesis only. If adipyl‐7‐ADCA hydrolysis and cephalexin synthesis were performed simultaneously and in combination with complexation with β‐naphthol, higher cephalexin concentrations also were found. In conclusion, a highly integrated process (two reactions simultaneously combined with in situ product removal) was shown possible, although further optimization is necessary. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 144–155, 2002.
Simulation of algae growth in a bench‐scale bubble column reactor
Authors: Wu Xiaoxi , Merchuk Jose C.
Published: September 2002

The growth of the marine red microalga Porphyridium sp. in a bubble‐column photobioreactor was simulated. The proposed model constitutes a dynamic integration of the kinetics of photosynthesis and photoinhibition with the fluid dynamics of the bubble column, including the effects of shear stress on the kinetics of growth. The kinetic data used in the model were obtained in independent experiments run in a thin‐film photobioreactor with defined light/dark cycles. The maintenance term was modified to take into account the effects of liquid flow in the bioreactor on the growth rate. A hybrid method proposed for the approximate solution of the equations gave an appreciable reduction of the calculation time. Extrapolations of the model indicated the possibility of predicting the optimal diameter for an assembly of bubble column photobioreactors. Satisfactory fit was found with the experimental results of biomass growth in a 13‐liter bubble column. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 156–168, 2002.
Determination of oxygen gradients in engineered tissue using a fluorescent sensor
Authors: Kellner Karin , Liebsch Gregor , Klimant Ingo , Wolfbeis Otto S. , Blunk Torsten , Schulz Michaela B. , Göpferich Achim
Published: September 2002

Nutrient and oxygen supply of cells are crucial to tissue engineering in general. If a sufficient supply cannot be maintained, the development of the tissue will slow down or even fail completely. Previous studies on oxygen supply have focused on measurement of oxygen partial pressures (pO2) in culture media or described the use of invasive techniques with spatially limited resolution. The experimental setup described here allows for continuous, noninvasive, high‐resolution pO2 measurements over the cross‐section of cultivated tissues. Applying a recently developed technique for time‐resolved pO2 sensing using optical sensor foils, containing luminescent O2‐sensitive indicator dyes, we were able to monitor and analyze gradients in the oxygen supply in a tissue over a 3‐week culture period. Cylindrical tissue samples were immobilized on top of the sensors. By measuring the luminescence decay time, two‐dimensional pO2 distributions across the tissue section in contact with the foil surface were determined. We applied this technique to cartilage explants and to tissue‐engineered cartilage. For both tissue types, changes were detected in monotonously decreasing gradients of pO2 from the surface with high pO2 to minimum pO2 values in the center of the samples. Nearly anoxic conditions were observed in tissue constructs (∼0 Torr) but not in excised cartilage discs (∼20 Torr) after 1 day. Furthermore, the oxygen supply seemed to strongly depend on cell density and cell function. Additionally, histological analysis revealed a maximum depth of ∼1.3 mm of regular cartilage development in constructs grown under the applied culture conditions. Correlating analytical and histological analysis with the oxygen distributions, we found that pO2 values below 11 Torr might impair proper tissue development in the center. The results illustrate that the method developed is an ideal one to precisely assess the oxygen demand of cartilage cultures. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 73–83, 2002.
Yield prediction and stoichiometry of multi‐step biodegradation reactions involving oxygenation
Authors: Yuan Zhiwen , VanBriesen Jeanne M.
Published: September 2002

Microorganisms can initiate the degradation of organic compounds by oxygenation reactions that require the investment of energy and electrons. This diversion of energy and electrons away from synthesis reactions leads to decreased overall cell yields. A thermodynamic method was developed that improves the accuracy of cell yield prediction for compounds degraded through pathways involving oxygenation reactions. This method predicts yields and stoichiometry for each step in the biodegradation pathway, thus enabling modeling a multi‐step biodegradation process in which oxygenations occur and intermediates may persist. EDTA and benzene biodegradation are presented as examples. The method compares favorably with other yield prediction methods while providing additional information of yields for intermediates produced in the degradation pathway. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 100–113, 2002.