摘要:

AbstractThe viscosity of bovine liver glutamate dehydrogenase solutions was studied at 10 and 20° C in 0.2.Msodium phosphate buffer at pH 7, in the concentration range 0.1–8 mg/ml. A method for the study of the viscosity of very dilute solutions of associating enzymes is described. It was found that the reduced specific viscosity ηsp/cof glutamate dehydrogenase continuously increases with increasing enzyme concentration, from about 4 ml/g at the lowest concentrations to about 16 ml/g at 8 mg/ml. In the presence of 10−3MGTP and 10−3MNADH the viscosity increase is much smaller and the results can be extrapolated to zero enzyme concentration to yield an intrinsic viscosity [η] = 3.2. The values of ηsp/cin phosphate buffer alone apparently extrapolate to the same value of [η], or to a value close to it. We also observe that, in the presence of toluene ηsp/cincreases very much more with enzyme concentration: ηsp/calready equals 16 ml/g at a concentration of 0.75 mg/ml. These observations are in good agreement with the hypothesis that the active oligomer of glutamate dehydrogenase (MW = 312,000) associates with increasing enzyme concentration to form linear rodlike polymers of indefinite length. This association is strongly diminished by the addition of 10−3MGTP, 10−3MNADH. Toluene, on the other hand, promotes reversible association to linear polymers of very high molecular weight. The transverse and axial rotary frictional coefficients of macroscopic bodies, similar to a physical model for the structure of glutamate dehydrogenase recently advanced, were determined. Assuming that the viscosity of the model is equal to that of an ellipsoid of rotation with identical frictional coefficients, we calculate [η] = 3.26 ml/g according to Kuhn and 3.20 ml/g according to Simha, for the glutamate dehydrogenase oligomer, in good agreement with the result derived from the study of

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractGlycogen acquires a negative charge in both alkaline and acidic solutions and can move in an electrical field, its mobility being related to the degree of alkalinity or acidity. There is a slight increase in relative viscosity at both ends of the pH spectrum. These effects and the changes in nuclear magnetic resonance as a function of pH are interpreted.

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe conformational transition of poly‐L‐tyrosine in 0.1MKCl 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 0.1NHCl 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 conf

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractMolecular monolaycrs of poly(β‐benzylL‐aspartate) spread at. an air‐water interface have been studied. The results obtained both by direct observations on the monlayer and from examination of collapsed films with polarized infrared spectroscopy and electron diffraction are consistent with the presence of right handed α‐helices in the mono‐layer when the molecular weight is high. When 1% (v/v) isopropanol is present in the subphase the right‐handed helix prevails, provided that the monolayer is first spread on water. Monolayers of low molecular weight polymer appear to form the crossed‐β structure. Orientated collapsed films of high molecular weight polymer can be converted to the left‐handed α‐helical and to the ω‐conformation, and the mechanisms are discussed. The surface chemistry of this polymer is compared with that of related polymers and a consistent pat

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe enthalpies of the helix‐coil transitions of the ordered polynucleotide systems of poly(inosinic acid)–poly(cytidylic acid) [poly(I + C)], (helical duplex), and of poly (inosinic acid) [poly(I + I + I)], (proposed secondary structure: a triple‐stranded helical complex), were determined by using an adiabatic twin‐vessel differential calorimeter. Measuring the temperature course of the heat capacity of the aqueous polymer solutions, the enthalpy values for the dissociation of the helical duplex poly (I + C) and the three‐stranded helical complex poly(I + 1 + 1), respectively, were obtained by evaluating the additional heat capacity involved in the conformational change of the polynucleotide system in the transition range. The ΔHvalues of the helix‐coil transition of poly (I + C) resulting from the analysis of the calorimetric measurements vary between the limits 6.5 ± 0.4 kcal/mole (I + C) and 8.4 ± 0.4 kcal/mole (I + C). depending on the variation of the cation concentration ranging from 0.063 mole cations kg H2O to 1.003 mole cations/kg H2O. The calorimetric investigation of an aqueous poly I solution (cation concentration 1.0 mole/kg H2O) yielded the enthalpy value ΔH= 1.9 ± 0.4 kcal/mole (I), a result which has been interpreted qualitatively following current models of inter‐ and intramolecular forces of biologically significant macromolecules. Additional information on the transition behavior of poly(I+ C)Was obtained by ultraviolet and infrared absor

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractAbsorption, circular dichroism (CD), and optical rotatory dispersion (ORD) measurements were carried out on poly‐L‐tyrosine in trimethyl phosphate solution over the spectral range 185–600 mμ. There is evidence in the CD spectrum for side chain‐side chain interactions in poly‐L‐tyrosine. ORD and CD data in dimethylformamide and pyridine closely parallel those in trimethyl phosphate, indicating a similarity in conformation of the polymer in all three solvents. In the polarized infrared spectrum both position and polarization of amide A, I, and II bands are characteristic of α‐helical polypeptides. Bands corresponding to side chain also exhibit dichroism, suggesting that the side chains are not randomly oriented. Viscosity and light‐scattering studies are consistent with α‐helical structure for the polymer that, remains rigid over a temperature range of 15–50°C and becomes somewhat flexible at higher temperatures. Optical rotatory properties were found to vary gradually and continuously with temperature over the range of −30 to +100°C. This suggested that all three electronic transitions of tyrosyl side chain are optically active, and that the side chains have some freedom of motion that decreases with decreasing temperature, disapp

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe structure of collagen is investigated by means of an energy minimization procedure. There is a rather broad trough of potential energy which involves a variety of structures (all collagen II type). It is seen that the unit height and the unit twist can strongly deviate from 2.86 Å, 36° values. Some of the good conformations are presente

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractPoly‐9‐vinyladenine was prepared by reaction of poly‐6‐chloro‐9‐vinylpurine with ammonia and poly‐1‐vinyluracil by hydrolysis of poly‐L‐vinyl‐2‐ethoxy‐4‐pyrimidinone. In aqueous solutions poly‐9‐vinyladenine shows hypochromism in the ultraviolet spectrum and forms a complex with polyuridylic acid as detected by a further decrease in the ultraviolet absorption. Under the same conditions, poly‐9‐vinyladenine and poly‐L‐vinyluracil inter

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe heal of solution of Poly‐ε‐carbobenzoxy‐L‐lysine and of a series of its copolymers with phenylalanine was measured as a function of solvent composition. The enthalpy change of the helix‐to‐coil transition was estimated for the various cases. The previous findings that side chains do not greatly affect the transition enthalpy is confirmed also in cases having much larger differences in hel

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090811

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY