摘要:

AbstractThe optical rotatory dispersion (ORD), and to a lesser extent the circular dichroism (CD) of the proteins tropomyosin and myosin have been extensively studied. The effect of aging and of certain reagents on these optical properties, relating to helical contents, were observed. As expected, spectra typical of right‐handed, α‐helices were found, with helical contents of 60–65% for myosin and 97–100% for tropomyosin. Studies were made to find which aqueous salt solutions would permit rotation observations in the far ultraviolet and also dissolve these proteins. The presence or absence of sulfhydryl groups (SH) were found to have no effect on helicity, and it is suggested that both proteins have an identical helical portio

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090102

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe aqueous phase of phenol extracts of HeLa cells contains polyglucose (CHO)n, RNA, and DNA. These macromolecules were precipitated together and removed from 50% (v/v) ethanol solutions with a stirring rod. The viscous precipitate had the classical white appearance of DNA, but contained an average of 439, 670, and 220 μg (from 3 × 107cells) of (CHO)n, RNA, and DNA, respectively. The (CHO)nwas separated from the RNA, either by CsCl density gradient centrifugation or by precipitating the RNA with trichloroacetic acid (TCA). Both methods of separation resulted in preparations of (CHO)nwith similar specific activities (radioactive counts/μg min). However, electron micrographs showed that the (CHO)nseparated by using TCA had a greater variation in particle size when compared with (CHO)nseparated by CsCl centrifugation. With the CsCl methods, the number‐average molecular weights, as determined by electron microscope particle‐counting, and the buoyant densities of (CHO)nwhose synthesis was stimulated by poliovirus infection and (CHO)nfrom noninfected cultures, were found to be similar. When the (CHO)nwas extracted from HeLa cells with TCA, rather than phenol, the yield was 1.68‐fold greater and its specific activity was an average of twice that of the (CHO)nextracted with phenol. The time at which cells were pulse‐labeled with14C‐glucose, after reducing the glucose in the culture medium to 0.01 of normal, was found to be important, in that the specific activity of the (CHO)nincreased 23.4‐fold over a 4‐hr period and the amount extracted decreased 8.2‐fold. The increase in the specific activities of RNA and DNA was not as large as that of the (CHO)nand the amounts extracted were not significantly changed. The sedimentation coefficients of RNA and (CHO)nwhich were separated from each other with TCA were 6.4 and 116 S, respectively, whereas, without separation, two peaks were seen, with values of 25.4 and 31.4 S. Chloride ions reduce the sensitivity of the Burton test for DNA. However, the Burton reagent will detect (CHO)neven in the presence of DNA if the assay mixture is heated. Chloride ions increase the sensitivity of the Burton reagent to detect melizitose and, at concentrations above l.5M, synthetic‐ polyglucose by increasing the absorption of the colored (CHO)

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090103

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe influence of inserting certain residues (X) into a polytripeptide sequence conformed into a poly‐L‐proline II helix is examined theoretically. It is found that for sequences such as ‐Gly‐Pro‐X‐ and ‐Gly‐X‐Pro‐, the introduction of glycyl,L‐alanyl orL‐seryl residues in the X position destabilizes the helix so that it is no longer the most stable intramolecular form. On the other hand,L‐prolyl andL‐hydroxyprolyl residues cause the PP II helix to be most stable. Of the many stable intramolecular forms, the majority will not pack efficiently to form fiber or solid‐state structures. The Rich‐Crick and Ramachandran collagen model structures were examined in terms of a Gly‐Pro‐Ala sequence, the Ramachandran, one‐hydrogen‐bond structure, being the most stable. However, another triple‐strand structure for (Gly‐Pro‐Ala)n, is much more energetically favorable. Hence, it may be concluded that none of the aforementioned is an entirely satisfactory collagen model. The new triple helix conformation proposed by Traub, Yonath, and Segal for (Gly‐Pro‐Pro) is found to give a more favorable intramolecular conformation for (Gly‐Pro‐Ala)nthan those derived from other collagen models. It is concluded that the collagen molecule derives its stability from interchain interactions in proline‐sparse r

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090104

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

年代:1970

数据来源: WILEY

摘要:

Abstractγ‐(l)‐MenthylL‐ andD‐glutamates were prepared by a fusion reaction ofN‐phthalyl‐L‐ andD‐glutamic anhydrides withl‐menthol, followed by hydrazinolysis. The monomers were polymerized to poly[γ‐(l)‐menthylL‐ andD‐glutamates] by theN‐carboxyanhydride method. These polymers were soluble in many organic solvents, such as ethyl ether, chloroform, tetrahydrofuran, andn‐hexane. From the results obtained by a study of the infrared absorption spectra, the x‐ray photographs, the optical rotatory dispersions and the circular dichroisms, poly[γ‐(l)‐menthylL‐glutamate] was found to be a right‐handed α‐helix in the solid state and in solution. Similarly, poly[γ‐(l)‐menthylD‐glutamate] was a left‐handed α‐helix. The helix‐coil transition of these polymers was observed in the vicinity of 40% dich

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090105

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe circular dichroism (CD) spectra of DNA–acridine orange (DNA–AO) complex in the visible region were measured at DNA phosphate‐to‐dye ratios (P/D) from 1 to 550. The CD spectrum of DNA–AO complex in the P/D ratio between 1 and approximately 40 consists of four components, i.e., positive CD bands centered at 510 and 480 mμ, and negative CD bands at 497 and 468 mμ. The CD bands at 510 and 468 mμ are optimum at P/D = 4, and the change of ε1− εrwith P/D suggests that both of them are induced from the interaction between dye molecules bound to adjacent DNA binding sites, each of which is composed of four nucleotides. This is supported by the fact that the values of ε1− εrfor both decrease with increasing temperature or increasing methylene blue concentration added to the complex. The negative Cotton effect at, 497 mμ is most favored at larger P/D ratio (∼8), and the suggested assignment is to the interaction between two dye molecules bound with an empty site between them. A positive Cotton effect at 480 mμ is observed at P/D ratio of less than 4 and is optimum at 1. Above P/D ratio of 40, the CD spectrum of the complex can not be resolved into its components and even at sufficiently high P/D ratio (550) the complex sho

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090106

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

年代:1970

数据来源: WILEY

摘要:

AbstractA diamide,N‐acetyl‐L‐proline‐N,N‐dimethylamide (AcProDMA), in water solution has optical rotatory dispersion (ORD) and circular dichroism (CD) spectra very similar to those of poly‐L‐proline II and the fibrous protein collagen. In contrast, AcProDMA in cyclohexane solution has optical activity resembling that of poly‐L‐proline I. Conformational analysis shows that AcProDMA is confined by steric constraints to either of two narrow regions of conformational space. Thetransisomer of AcProDMA assumes conformations near those of polyproline II and collagen nearest neighbors, whilecis‐AcProDMA assumes conformations near that of polyproline I nearest neighbors. Nuclear magnetic resonance (NMR) experiments show that an equilibrium mixture of thecisandtransisomers of AcProDMA is present in solution. Thetransisomer predominates in aqueous solution, but the equilibrium shifts to favor thecisisomer in nonpolar organic solvents such as cyclohexane. Analysis of the ORD spectra in terms of two basic spectra reveals a solvent dependent isomerization which parallels that observed by NMR. The optical activity of the pure isomers of AcProDMA can be derived from the ORD, CD and NMR data. A comparison of component cotton effects confirms the similarity in optical activity oftrans‐AcProDMA, polyproline II, and collagen on the one hand, and ofcis‐AcProDMA and Pol

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090107

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

年代:1970

数据来源: WILEY

摘要:

AbstractUnfractionated yeast transfer ribonucleic acid (tRNA) was reacted in aqueous acetone solution with the sulfhydryl spin‐labeling reagnent,N‐(l‐oxyl‐2,2,5,5‐tetramethyl‐3‐Pyrrolidinyl)iodoacetamide. Whereas tRNA stripped of amino acids reacted only slowly, there were sites on tRNA charged with cysteine which combined rapidly with the reagent. The latter class of spin‐label was quickly cleaved from the tRNA upon incubation in mildly alkaline solution (pH 8.0), suggesting that it was attached to the cysteinyl side chains. The paramagnetic resonance spectrum of column‐purified spin‐labeled cysteinyl tRNA showed that the spin‐label was partially immobilized as a result of its interaction with the tRNA. When the tRNA was slowly heated, an abrupt increase occurred in the rotational mobility of the paramagnetic

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090108

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

年代:1970

数据来源: WILEY

摘要:

AbstractWe investigate the time‐dependent solution of a set of equations used to approximate the binding of flexible polymers to the surface of suspended targets. The equations account, for the possibility that the first adsorption step can be a rate limiting step. Rate constants for other steps of adsorption and desorption are proportional to the number of free and occupied polymer binding sites, respectivel

ISSN:0006-3525    

DOI:10.1002/bip.1970.360090109

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.1970.360090110

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.1970.360090111

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

年代:1970

数据来源: WILEY