摘要:

AbstractThe viscosity–temperature behavior of N4 virus solution was investigated by using a Zimm type viscometer. The role of ionic strength (LiBr) and pH in the viscosity–temperature behavior was determined. Supporting measurements of the sedimentation coefficient, infectivity, and optical density are presented. The viscosity–temperature behavior generally includes a region of low viscosity, characteristic of the intact virus, followed, upon increasing temperature, by a rather abrupt increase of viscosity which corresponds to the ejection of native DNA from the protein shell, presumably through a suitable opening in the capside. The viscosity remains constant upon further increase of temperature until a second abrupt increase is observed which is shown to correspond to the degradation of the empty protein shell (ghost). Finally, at a still higher temperature, denaturation of DNA occurs. This sequence of events can be altered by changes in pH and ionic strength. Increasing LiBr concentration reduces the temperature of ghost degradation and raises the temperature of DNA ejection and DNA de naturation. It is suggested that polyelectrolyte effects play a controlling role in the ejection of native DNA and that the conformation of the latter within the protein shell is stabilized by a decrease of the electrostatic free energy due to the swamping effect of the co

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080602

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

年代:1969

数据来源: WILEY

摘要:

AbstractA 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.

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080603

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

年代:1969

数据来源: WILEY

摘要:

AbstractAn exchange method is described for producing tritium‐labeled native DNAin vitrowith minimal physical damage to the DNA. Tritium‐labeled calf thymus DNA prepared in this way has a specific activity of about 100 μCi/mmole of nucleotide (i.e., about 2 × 108dpm/mmole). Sedimentation velocity at neutral and alkaline pH indicate that the product has an average of two single strand breaks per duplex molecule of molecular weight 6 × 106daltons. The optical and thermal denaturation properties of the product are those of native DNA. The method should be particularly useful for labeling DNA from organisms that cannot be labeled convenientlyi

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080604

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe binding of pancreatic ribonuclease‐A by denatured DNA, native DNA, poly‐dA, and poly‐dT, has been studied by a gel filtration method. With denatured DNA at pH 7.5, ionic strength 0.053M, there is one binding site per 12 nucleotides and the equilibrium binding constant per site is 9.7 × 104l./mole. The binding constant increases by a factor of 8 as the pH is decreased from 8 to 7. The strength of the binding of denatured DNA increases with decreasing ionic strength. At pH 7.5, native DNA binds about ⅛ as strongly as does denatured DNA. The binding affinity increases in the order poly‐dA, denatured DNA, and poly‐dT. These results support the view that the binding of denatured DNA involves both electrostatic interactions between the negatively charged polynucleotide and the positively charged protein, and an interaction of the protein with a pyrimidine residue of the denatured DNA, and thus that the binding is basically similar to that between RNAse and its s

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080605

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

年代:1969

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the molecular origin of the dipole moment of sperm whale myoglobin as it can be calculated from the dielectric dispersion at 1 Mcps on the basis of a mechanism of orientational polarization. It was possible to compare the dielectric increment of native myoglobin and its change during the reaction with bromo acetate with dipole moments calculated according to the known coordinates of the charged groups of the molecule. The agreement between the two shows that in myoglobin only the permanent dipole moment due to these charged groups is important, and that contributions from other possible sources remain within the limits of experimental error.

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080606

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe binding of proflavine to DNA has been studied by measuring the polarization and intensity of emission of DNA–dye complexes. Such measurements also permit the determination of the fluorescence of the bound dye as a function of the degree of binding. Techniques of emission spectroscopy permit the study of complexing at high phosphate to dye ratios, and we have examined complexes formed at up to 12,300:1 phosphates to dye. At high phosphate to dye ratios, we find that equilibrium plots of the binding data show only one type of binding. Reports in the literature of multiple binding constants are shown to be due to the incorrect assumption that the fluorescence of the bound dye is independent of the amount bound. The emission properties can be qualitatively accounted for by assuming that nearest‐neighbor interaction between bound dyes quenches the fluorescence. We report that, within experimental error, the binding constant is insensitive to the base content of the DNA. The DNA‐dye complexes show a temperature dependent depolarization, the cause of which is, as yet, unknown. Heat denaturation of the DNA–dye complex may be followed on a Perr

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080607

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

年代:1969

数据来源: WILEY

摘要:

AbstractMechanical inciting experiments performed on collagen fibers were used to study the effect of crosslinking on contraction kinetics. With the aid of a two‐state model it is shown that the degree of cooperativity of this dematuration process is increasing with the degree of crosslinkin

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080608

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

年代:1969

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.1969.360080601

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

年代:1969

数据来源: WILEY