bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of synthetic polymers of amino acids to knowledge of immune response
Authors: Maurer Paul H. , Babu Uma Mahesh , Lai Chang‐Hai 
Published: December 2004

AbstractThe synthetic random polymers poly(Glu,Lys,Phe), poly(Glu,Phe) and poly(Glu,Lys,Tyr), have been used to study some parameters associated with the genetic control of the immune response (Ir) of mice. Mice of haplotypes d and q respond well to GLPhe. Mice of haplotypes k and b were previously shown to be nonresponders, whereas the F1 (k × b) responded via a phenomenon involving “complementation” between 2 Ir genes, i.e., one gene product from IA, and another from IE form the requisite two‐chain Ia “receptor” macromolecules (EE). When it was determined that mice of haplotypes q and k respond to GPhe, and the controlling gene maps to IA, (Aα Aβ), we tested the theory that mice having q and k alleles in IA might respond to GLPhe via recognition of GPhe determinants in the terpolymer. Employing the in vitro proliferative response to T‐cells from mice immunized with GLPhe and stimulated with GPhe and GLT (cross‐reaction), it was determined that different determinant selection patterns exist in the recognition of GLPhe. Mice having q and k alleles in IA can respond to GLPhe via one mechanism, and other mice having d and f alleles respond via other mechanisms. The F1 of the appropriate nonresponder strains forming the Ia molecule (EE) still exhibit the “complementation” phenomenon. Rabbit antibody against anti‐GPhe (ID) from SWR mice (H‐2q)(anti‐ID) was prepared. This anti‐ID strongly inhibited the binding of 125I‐GPhe by anti‐GPhe antisera produced only in mice of H‐2q haplotype and had no effect on the binding of GPhe by anti‐GPhe antisera produced in mice of other haplotypes. The anti‐ID also inhibited the binding of 125I‐GLPhe and 125I‐GPhe by anti‐GLPhe antisera produced only in mice of H‐2q haplotype. These specificities were also confirmed by the inhibition of the plaque‐forming cells. It was concluded that the antibodies produced in mice of H‐2q haplotype against GPhe and GLPhe share common idiotypic determinants that are recognized by the anti‐idiotypic antiserum.
The T‐cell receptor as analyzed by functional T‐cell lines specific to a synthetic polypeptide antigen
Authors: Mozes Edna 
Published: December 2004

AbstractFor a better understanding of the molecular nature of the antigen‐specific T‐cell recognition system, continuous T‐cell lines specific to the synthetic polypeptide antigen poly(Tyr,Glu)‐poly(DLAla)‐‐poly(Lys) [(T,G)–A‐‐L] were established from C3H.SW (high‐responder) activated T‐cells, cloned, and characterized. These lines and their derived clones are also constitutive secretors of antigen‐specific T‐cell replacing helper factors. The secreted T‐cell helper factor was shown to possess MHC determinants as well as V‐region determinants, or more specifically, idiotypic determinants that are cross‐reactive with those expressed on (T,G)–A‐‐L‐specific antibodies of the same mouse strain. Using the fluorescence‐activated cell sorter (FACS II) and individual C57BL/6 anti‐idiotypic sera produced against (T,G)–A‐‐L‐specific antibodies of C3H.SW origin, we have demonstrated the expression of the cross‐reactive idiotypic markers on the monoclonal helper T‐cells. Attempts were made to purify the active fraction of the T‐cell factors secreted by the (T,G)–A‐‐L continuous helper lines. Gel analysis of the twice affinity‐purified eluate of a (T,G)–A‐‐L column revealed the existence of iodinated bands with molecular weight of 17,000 and 15,000, in addition to a diffuse band of high molecular weight. The specific helper activity of the factors was associated with a 65–75% ammonium sulfate precipitate. Gel electrophoresis of the latter fraction, as well as of an eluate of a (T,G)–A‐‐L–Sepharose column indicated that a high‐molecular‐weight (< 67,000) and a low‐molecular‐weight (15,000–17,000) fraction contained the biological activity of the factor. Similar results were obtained following chromatography of the factor on Sephadex G‐100 columns. The two fractions were shown to be synthesized by the T‐cell lines, as indicated by internal labeling experiments using 35S‐methionine. Thus, it is suggested that a fraction of an apparent molecular weight of 15,000–17,000 preserves both the antigen specificity and the helper activity of the factor produced by the (T,G)–A‐‐L‐specific T‐cell lines.
Some novel approaches to the design and synthesis of peptide–catecholamine conjugates
Authors: Verlander M. S. , Jacobson K. A. , Rosenkranz R. P. , Melmon K. L. , Goodman M. 
Published: December 2004

AbstractA series of novel, functionalized catecholamines (congeners) has been synthesized in which, formalistically, the N‐isopropyl group of isoproterenol has been extended by a linear alkyl chain of varying length, terminated by a carboxyl group. Model amide derivatives have also been prepared in order to optimize the biological activity of these derivatives and also to aid in the design of appropriate peptides for the synthesis of conjugates. As a result of these studies, a series of amino acid and monodisperse peptide carriers, containing p‐aminophenylalanine as the point of attachment for the drug, was prepared, together with the corresponding conjugates. In vitro and in vivo evaluation of the congeners, model amides, and conjugates has demonstrated that the biological activity of these derivatives is extremely sensitive to structural modifications at a point far‐removed from the pharmacophore, in both the congener amide and conjugate series. A number of the model amides and conjugates have proven to be highly active when tested in both in vitro and in vivo test systems. The implications of these results in terms of a novel structure–activity approach to drug design are discussed.
Synthesis and biological activity of (D)Ala2, Leu5‐enkephalins containing hydrophilic or hydrophobic moieties
Authors: Filippi Bruno , Biondi Laura , Filira Fernando , Rocchi Raniero , Bellini Cecilia , Sarto Giampietro 
Published: December 2004

AbstractThe synthesis in solution of some modified (D)Ala2,Leu5‐enkephalins has been carried out. The lipophilic properties of the parent compound have been modified by amidation of the carboxyl function with alkylamines of increasing hydrophilicity to increase permeability of the blood‐brain barrier. Attempts to reduce enzymatic degradation have been carried out either by reductive glucosamination or by amidation of the carboxyl function with 2‐amino‐2‐deoxy‐β‐D‐glucopyranose. Esterification of the carboxyl function of (D)Ala2,Leu5‐enkephalin with polyethylenglycole 1000 has also been carried out. The effects induced by these modifications have been evaluated by in vitro and in vivo tests.
Centrifugal field relaxation and ionic strength effects on calf thymus DNA gels
Authors: Richard Alfred J. 
Published: December 2004

AbstractThe gellike phase formed by DNA on sedimentation to the bottom of a centrifuge cell has been studied as a function of centrifuge speed and of solvent ionic strength. The swelling pressure of the gel was found to be logarithmically related to the DNA concentration and also to the ionic strength of the solvent. The concept of electrostatic persistence length was useful in interpreting the gel‐phase volume changes occurring with ionic strength.
1H‐nmr studies on the dinucleoside monophosphates containing 2′‐halogeno‐2′‐deoxypurinenucleosides: Effects of 2′‐substitutes on conformation
Authors: Uesugi Seiichi , Kaneyasu Toshinori , Imura Junko , Ikehara Morio , Cheng Doris M. , Kan Lousing , Ts'o Paul O. P. 
Published: December 2004

AbstractSeven dinucleoside monophosphates containing 2′‐halogeno‐2′‐deoxypurine nucleoside residue, dAfl‐U, dAcl‐U, dAbr‐U, dAio‐U, dGfl‐U, and dIfl‐C, were chemically synthesized and investigated by 1H‐nmr spectroscopy at 300 MHz. The sugar and backbone conformations of these compounds were analyzed by the spectral pattern of furanose proton resonances; and the extents of base‐base interaction were estimated from chemical shifts and their temperature‐dependent changes of base‐proton resonances. It is found that the population of C3′‐endo conformer and the extent of base‐base interaction decrease as the electronegativity of 2′‐substituent decreases in dAx‐U (x = fl, cl, br, and io) series. The C3′‐endo (3E) population and the base‐base interaction in Nfl‐U (N = A,G)‐type dimers as well as dIfl‐C are relatively higher than the corresponding natural ribo‐dimers but can be recognized as grossly similar to the conformation of regular RNA dimers.
Conformation of sequential and random copolypeptides of lysine and alanine in sodium dodecyl sulfate solution
Authors: Kubota Shigeo , Ikeda Kiyoshi , Yang Jen Tsi 
Published: December 2004

AbstractA series of sequential polypeptides, (Lysi‐Alaj)n, and random copolypeptides, (Lysx, Alay)n, were synthesized. The competitive effect of Ala, a helix former, and Lys, whose homopolymer has a β‐form in neutral NaDodSO4 solution, was determined by CD and absorption spectroscopy. All the polypeptides studied were unordered in neutral solution without the surfactant. Of the six sequential polypeptides only (Lys‐Ala)n adopted a stable β‐form in NaDodSO4 solution. Most striking is the difference between this polypeptide, (Lys2‐Ala2)n and (Lysx, Alay)n, even though they all have equimolar Lys and Ala. (Lys2‐Ala2)n was partially helical in 2.5–5 mM NaDodSO4 but approached the unordered form in 50 mM NaDodSO4, whereas (Lys50, Ala50)n was completely helical in all NaDodSO4 concentrations. Even Lysrich (Lys2‐Ala)n and (Lys3‐Ala)n formed a partial helix and a trace of the β‐form, respectively, in low NaDodSO4 concentrations; both reverted to the unordered form in high NaDodSO4 concentrations. These results can be explained by Pauling‐Corey's model for β‐pleated sheets. Only (Lys‐Ala)n has all DodSO‐bound Lys+ residues on one side and Ala residues on the other side of the polypeptide chain. They can nestle quiet efficiently in a β‐sheet and between neighboring β‐sheets. Our results further imply that random copolypeptides are not completely random; they comprise varying segments of (Lysk‐Alam), where k and m could vary from zero to a small integer.
Complex formation with alkali and alkaline earth metal ions of cyclic octapeptides, cyclo(Phe‐Pro)4, cyclo(Leu‐Pro)4, and cyclo[Lys(Z)‐Pro]4
Authors: Kimura Shunsaku , Imanishi Yukio 
Published: December 2004

AbstractComplex formation with alkali and alkaline earth metal ions of cyclic octapeptides, cyclo(Phe‐Pro)4, cyclo(Leu‐Pro)4, and cyclo[Lys(Z)‐Pro]4 was investigated in relation to conformation. In an alcohol solution, cyclo(Phe‐Pro)4 did not form complexes. However, cyclo(Leu‐Pro)4 and cyclo[Lys(Z)‐Pro]4 formed complexes selectively with Ba2+ and Ca2+ ions. Changing the solvent from alcohol to acetonitrile, the complexation behavior was very different. In acetonitrile, cyclo(Phe‐Pro)4 was found to form a complex with Ba2+, and CD spectra of cyclo(Leu‐Pro)4 and cyclo[Lys(Z)‐Pro]4 changed sharply on complexation with K+. Rate constants of the complex formation between the cyclic octapeptides and metal salts were in the range of 0.7–12 L mol−1 min−1 in an alcohol solution. One of the two types of complex formation in acetonitrile was much faster than that in an alcohol solution.
Heat capacity increments: Conformational transitions in polypeptides
Authors: Couchman P. R. , Gajnos G. E. , Ryan C. L. , Karasz F. E. 
Published: December 2004

AbstractA thermodynamic treatment of the helix–coil transition of synthetic polypeptides in binary organic solvent mixtures is extended to describe isobaric heat‐capacity increments associated with the phenomenon. This development resolves such increments into three components: two associated respectively with intrinsic differences between the ordered and disordered states of the macromolecule and between the coil–solvent complex and its components, and a third term derived from the temperature dependence in the fraction of coil residues bound to active solvent. Insights derived from this analysis are also applied to the discussion of some heat capacity increments associated with the denaturation of globular proteins.
Low‐frequency Raman scattering by anharmonic DNA modes with A⇌B character modeled with a classical double‐well oscillator
Authors: Martin A. J. 
Published: December 2004

AbstractThe optical modes of DNA that displace one strand against the other are modeled by the motion of an oscillator in an asymmetric quartic double‐well potential whose minima represent the A‐ and B‐conformations. Assuming that the variation of the polarizability during vibration derives mainly from the tilting of the base rings relative to the helix axis, the total polarizability tensor is shown to possess approximately ellipsoidal symmetry and to depend nonlinearly on the instantaneous displacement of the two strands. The Raman spectrum of a collection of randomly oriented molecules is calculated. It consists of one or more peaks with characteristic shape. The depolarization ratio is 3/4, independent of molecular conformation and frequency. The results are discussed in the light of existing experimental and theoretical information.
31P‐NMR studies of deoxyoligonucleotides
Authors: Cheng Doris M. , Kan Lou‐Sing , Iuorno Virginia L. , Ts'O Paul O. P. 
Published: December 2004

AbstractThe assignments of 31P resonances of eight short oligonucleotides have been achieved through specific heterodecoupling techniques reported previously from our laboratory [Cheng et al. (1982) Biopolymers 21, 697–701]. The temperature dependence of the assigned 31P chemical shifts of these oligomers was studied and compared to the constitutive dimeric units. This comparison gives some insight to the chemical‐shift values of the phosphorus resonances of oligonucleotides. (1) The 3′‐end terminal phosphorus resonance in an oligomer tends to locate at a spectral position relatively close to its constitutive dimeric unit. (2) On chain elongation (from 5′‐toward 3′‐end), the phosphorus resonance in the oligomer will be shifted upfield by 0.2–0.3 ppm, as compared to its constitutive dimeric unit. (3) The relative positions of phosphorus resonances in an oligomer tend to remain in the same order as their constitutive dimeric units. The above obsrvations lead to the development of a new procedure to assign the 31P resonance of a single‐stranded oligonucleotide.
Conformational studies of adenosine 5′‐phosphorodiamidates in aqueous solution
Authors: Tomasz Jenö , Barabás Klára , Bottka Sándor , Kajtár Judit , Kajtár Márton , Kajtár‐Peredy Mária , Radics Lajos 
Published: December 2004

AbstractCD and nmr studies show that the conformational equilibrium of N(P)‐alkylated adenosine 5′‐phosphorodiamidates 2–4 and, to a much lesser extent, adenosine 5′‐phosphorodiamidate 1 differ at two parts from that of adenosine 5′‐phosphate in water. The glycosidic bond conformation is slightly shifted into the direction of the syn range, and the ribose ring N‐conformer population increases. The conformational changes increase with increasing degree of N(P)‐alkylation and cause a change of the sign of the long‐wavelength CD band for 2–4. The new conformation may be characterized by a stacked arrangement for the adenine ring and the 5′‐substituted phosphate group of 2–4. Hydrophobic attraction between the head and the tail of the molecules, as well as the entropy effect (which promotes the clustering of apolar faces in water), may be jointly responsible for this stacked arrangement. The intramolecular attractive forces stabilizing the stacked conformation may act at the expense of the solubility decreasing intermolecular attractive forces, and may thus be responsible for the increased water solubility of 2–4, which is higher than that of 1 by more than two orders of magnitude.
Aggregation of poly(γ‐benzyl‐α,L‐glutamate)
Authors: Chakrabarti Sumana , Miller Wilmer G. 
Published: December 2004

AbstractThe aggregation of poly(γ‐benzyl‐α,L‐glutamate) and its enantiomer in toluene has been investigated by following the viscosity as a function of temperature, concentration, molecular weight, molecular‐weight distribution, helix chirality, and shear rate. The temperature and concentration data for a 138,000‐molecular‐weight sample was fitted to an open, reversible end‐to‐end aggregation model. The aggregation numbers resulting from this fit were consistent with the sudden onset in non‐Newtonian flow resulting from only a 0.2‐wt% increase in concentration. The association equilibrium constant was then used to predict viscosity for comparison with other data, in particular, the effect of molecular weight and molecular‐weight distribution. A mixture of right‐and left‐handed helices showed the aggregation was not chiral selective. The stiffness of end‐to‐end aggregated (hydrogen‐bonded) molecules differed little from their covalent counterparts, at least below a molecular weight of ∼106. We conclude that polybenzylglutamate aggregation in toluene can be described by an open end‐to‐end aggregation model.
The titratable joint phenomenon in ΦW‐14 DNA
Authors: Wilcoxon Jess , Schurr J. Michael , Warren R. A. J. 
Published: December 2004

AbstractDynamic light scattering (DLS) studies are carried out on native ΦW‐14 DNA, which has putrescines covalently attached at the methyl groups of half its thymines, and on a chemically modified form of the same DNA in which the ammonium groups of its putrescines are almost completely acetylated. From neutrality to pH 9.6, both forms of ΦW‐14 DNA exhibit the same curve of Dapp vs K2 over the range K2 = 0.5 × 1010 to K2 = 20 × 1010 cm−2, and this coincides with curves that we have observed for other DNAs. (Dapp, apparent diffusion coefficient; K, scattering vector). However, when the pH is raised to pH 10.0–10.2, native ΦW‐14 exhibits a spectacular decrease in Dapp at large wave vector, whereas the acetylated form shows no sign of such behavior. It is inferred that bound ammonium groups make an essential contribution to the stabilization of titratable joints. Comparing the pH profiles of the absorbance (A260) for these two DNAs gives some evidence that base unstacking may be involved in titratable joint formation.
Interaction of poly‐5‐bromouridylic acid. II. Thermodynamic analysis of its interaction with adenosine and 9‐methyladenine
Authors: Higuchi Shigesada , Yasui Kumiko 
Published: December 2004

AbstractThe interaction of poly‐5‐bromouridylic acid [poly(BU)] with adenosine and 9‐methyladenine was studied by equilibrium dialysis, optical melting, and microcalorimetry. The stacking free energy, ω, was estimated as −17.6 kJ/mol for adenosine·2poly(BU) and −18.8 kJ/mol for 9‐methyladenine·2poly(BU) from the binding isotherms constructed from equilibrium dialysis results. The binding isotherms constructed from a series of melting curves also gave ω values for adenosine·2poly(BU). The thermal stability of the complex depends on monomer concentration, and the partial molar enthalpies of the complex formation at the midpoint of the transition were evaluated from the Tm coefficients as a function of free monomer concentration. The values of −92.0 and −90.4 kJ/mol were obtained for adenosine·2poly(BU) and 9‐methyladenine·2poly(BU) in 0.4M NaCl–0.02M Na‐cacodylate–5 × 10−4M EDTA (pH 7.0), respectively. Microcalorimetric measurements provided lower integral heats of reaction values for these complexes, i.e., −73.2 kJ/mol for adenosine·2poly(BU) and −71.5 kJ/mol for 9‐methyladenine·2poly(BU). A comparison with a polyribouridylic acid system provided a quantitative understanding of a stabilization by bromination in terms of thermodynamic parameters.
Proton‐NMR study of the interaction of trans‐dichloro‐diamine‐platinum(II) with poly(I) and poly(I)·poly(C)
Authors: Fazakerley G. Victor , Hermann Dominique , Guschlbauer Wilhelm , Hawkes Geoffrey E. 
Published: December 2004

AbstractThe fixation of trans‐(NH3)2Cl2 Pt(II) to poly(I)·poly(C) at low rb (< 0.05) leads to the formation of two complexed species. The major species (ca. 82% of bound platinum) involves coordination of platinum to a single hypoxanthine base, while the other species involves coordination of two hypoxanthine bases, which are either far apart on the same strand or on separate poly(I) strands, to the platinum. These same two species are found after reaction with poly(I), as are two other species throughout the entire rb range studied (rb = 0–0.30). The latter two species are assigned to trans‐Pt bound to two bases on a poly(I) strand with (a) one or (b) two free bases between the two bound bases. These two species, (a) and (b), account for ca. 35% of the bound platinum, although the 1:1 species remains dominant (ca. 55%). These two additional species are observed at high rb (>0.075) after reaction with poly(I)·poly(C) but as very minor species. They are formed by reaction with melted poly(I) loops. Also at high rb, we have observed a shifted cytidine H5 resonance arising from interaction of trans‐Pt with a melted loop of poly(C). Most probably, this arises from an intramolecular poly(I) to poly(C) crosslink. Results from the reaction of trans‐Pt with poly(C) are presented for comparison.
Monoazido analog of ethidium as a chromatin probe: Binding to DNA
Authors: Coffman George L. , Yielding Lerena W. , Yielding K. Lemone 
Published: December 2004

AbstractTwo photoaffinity analogs of ethidium, 8‐azido‐3‐amino, and 3‐azido‐8‐amino‐5‐ethyl‐6‐phenylphenanthridinium chloride, have been used to probe the structure of mammalian chromatin and its interactions with the ethidium moiety. The monoazido analogs were established as suitable probes by comparing their interactions with chromatin and pure DNA prepared from chromatin to those of the parent ethidium bromide. Scatchard analysis of the binding data determined from spectrophotometric titrations showed that the analogs interacted with both nucleic acids in a manner similar to the parent compound. The effect of chromatin proteins on the interaction of the ethidium moiety with intact chromatin was investigated directly. By exposing the noncovalent complex to visible light, the monoazido analog was attached covalently in its interaction sites within chromatin, and the amount of drug bound covalently to DNA was determined for both protein‐free DNA and chromatin. Using saturating concentrations of drug, DNA within intact chromatin was found to be associated with only half as much drug as DNA extracted from its protein prior to drug exposure. The distribution of drug bound within chromatin was determined following the attachment of the monoazido analog (by photoactivation) to chromatin that had undergone limited nuclease digestion. Several distinct populations isolated by size fractionation and quantitative measurements revealed that (1) both the core particles and the spacer‐containing particles contained bound drug, reflecting high‐affinity binding sites; and (2) chromatin particles containing 150 DNA base pairs (putatively nucleosome core structures) contained less total bound drug at high drug concentrations than those particles having intact spacer DNA.