ISSN:0006-3525    

DOI:10.1002/bip.360250902

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

年代:1986

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360250903

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

年代:1986

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360250904

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

年代:1986

数据来源: WILEY

摘要:

AbstractX‐ray diffraction studies have been carried out on a single crystal of the photosynthetic inhibitors N‐(3,4‐dichlorophenyl)‐N′‐dimethylurea (DCMU) and its newly synthesized spin‐labeled analog N‐(3,4‐dichlorophenyl)‐N′‐(3,3,5,5‐tetramethylpiperidine‐4‐oxyl)‐urea (DTPU). The synthesis of DTPU as well as its crystallographic data are reported. The crystal system of both compounds is monoclinic with a space groupP21/c. The cell constants of DCMU area= 7.759(1),b= 14.737(3),c= 9.233(2) Å, β = 100.99(6)°; of DTPU they area= 6.976(1),b= 11.998(2),c= 23.585(3) Å, β = 91.38(5)°. Comparison of conformational parameters of DCMU and DTPU reveal differences in the dihedral angle between the aromatic ring and the ureido plane. The measured volumes of DCMU and DTPU are 259.1 and 493.3 Å3, respectively. These figures suggest the size of the binding site of the inh

ISSN:0006-3525    

DOI:10.1002/bip.360250905

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe interpretation of ΔG DH 2O(the free energy change for the reaction, globular conformation ⇋ randomly coiled conformation, in the absence of denaturant), in terms of the free energies of transfer of various parts of the protein molecule from water to denaturant solution, is unsatisfactory because the latter are assumed to be identical to the transfer‐free energies of similar groups attached to smaller model compounds. We have made empirical adjustments to transfer‐free energy theory that make possible linear extrapolation of the free energy of denaturation of a protein from transition region to zero denaturant concentration. The modified theory, used to analyze the denaturation of proteins by guanidine hydrochloride and urea, allowed us to calculate reasonable values for Δα, the average change in accessibility to solvent of the component group

ISSN:0006-3525    

DOI:10.1002/bip.360250906

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe conformational analysis of a protected homodipeptide of 1‐aminocyclopentanecarboxylic acid (Acc5) has been carried out.1H‐nmr studies establish a β‐turn conformation for Boc‐Acc5‐Acc5‐NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X‐ray diffraction studies reveal a type III β‐turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The ϕ,ψ values for both Acc5residues are close to those expected for an ideal 310‐helical conformat

ISSN:0006-3525    

DOI:10.1002/bip.360250907

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

年代:1986

数据来源: WILEY

摘要:

AbstractBovine pancreatic trypsin inhibitor (BPTI) was reductively alkylated with 2‐methoxy‐1‐naphthyl aldehyde and sodium cyanoborohydride (NaCNBH3). All five possible derivatives, each labeled at one of the primary amino groups of BPTI, were obtained. The distribution of yields of the various derivatives can be controlled by changing the reaction conditions. Products were identified by high‐performance liquid chromatography (HPLC) tryptic peptide mapping. This procedure was used for the preparation of three pure 2‐methoxy‐1‐naphthyl‐methylenyl‐BPTI (MNA‐BPTI) derivatives. Purification was achieved by means of affinity chromatography and HPLC. The spectral characteristics of the probe, notably monoexponential decay with a lifetime of 6.8 ± 0.1 ns and moderate limiting fluorescence polarization,P= 0.3 ± 0.015, make it a very useful donor in energy

ISSN:0006-3525    

DOI:10.1002/bip.360250908

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe multidimensional statistical technique of discriminant analysis is used to allocate amino acid sequences to one of four secondary structural classes: high α content, high β content, mixed α and β, low content of ordered structure. Discrimination is based on four attributes: estimates of percentages of α and β structures, and regular variations in the hydrophobic values of residues along the sequence, occurring with periods of 2 and 3.6 residues. The reliability of the method, estimated by classifying 138 sequences from the Brookhaven Protein Data Bank, is 80%, with no misallocations between α‐rich and β‐rich classes. The reliability can be increased to 84% by making no allocation for proteins classified with odds close to 1. Classification using previously developed secondary structural prediction methods is considerably less reliable, the best result being 64% obtained using predictions based on the De

ISSN:0006-3525    

DOI:10.1002/bip.360250909

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe mobility of solvent associated with native DNA in comparison with that of the bulk solvent is monitored from the temperature‐dependent red shift in the phosphorescence spectra of acridines bound to DNA and free in glycol–buffer mixtures. Over the temperature range for which the red shift occurs the phosphorescence decay changes with emission wavelength, indicating the time‐dependent nature of the process. Moreover, at these temperatures, emission anisotropy measurements establish that motions of the dye itself are not involved. Correspondence between perturbations to the solvent that influence the temperature at which the red shift occurs for free acridine with those for the DNA‐bound dye confirm that “bound solvent” is responsible for the spectral changes. For the DNA‐bound acridines the extent of the red shift is smaller and the midpointT1/2of the transition is warmer. The reduction in the red shift reveals that the bound dye is less exposed to solvent and varies as 9‐aminoacridine

ISSN:0006-3525    

DOI:10.1002/bip.360250910

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe decrease in mobility of viscous glycol–water solvents when associated with native DNA is quantified from a study of the loss of the exciting‐wavelength dependence of the phosphorescence spectrum of free and bound proflavin with increasing temperature. The data are interpreted in terms of a distribution of rate constants with an Arrhenius temperature dependence. Over the temperature range of the experiments a relative decrease of ∼ 104in the average rate constant is observed for reorientation of the solvent when associated with DNA. The basis for this large reduction is found to derive from a large decrease in the pre‐exponential factors (i.e., activation entropy) associated with the reorientation rate constants. The changes in the distribution of rate constants and the activation parameters for solvent mobility induced by DNA do not resemble the changes observed for any one of a number of small ion or molecule perturbations. The results suggest the presence of disorganized, relatively immobile solvent in association w

ISSN:0006-3525    

DOI:10.1002/bip.360250911

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

年代:1986

数据来源: WILEY