摘要:

AbstractThe interaction of water with collagenous tissue was investigated using dynamic mechanical spectroscopy and cryogenic X‐ray techniques. The loss spectrum was found to be very sensitive to water which is highly associated with the macromolecule. Two water‐sensitive loss peaks were observed below 0°C: the β2or “water dispersion” at 150°K and the β1at 200°K which is attributed to motion of polar side chains. Changes in peak temperature and intensity were not continuous with water content, but exhibited regimes in behavior which were associated with two types of nonfreezable water, structural and bound water. In cryogenic X‐ray experiments, specimens which contained some freezable water exhibited reflections identified with the cubic form of ice. These ice crystals underwent an irreversible transition to the more common hexagonal form when warmed above 200°K. On the basis of these experiments, a model for the hydration of native collagenous tiss

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160202

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe properties of triple‐helix formation of (Pro‐Pro‐Gly)nwere studied. The probability of hybridization between the polytripeptides (Pro‐Pro‐Gly)n, of different degrees of polymerization was investigated by gel filtrations of mixed solutions of them. Using samples selectively labeled with radioactivity, the elution pattern was detected by uv absorption and liquid scintillation counting. The hybridization was found only when the difference of polymerization is small. The amount of heterohelices (triple helices of the polypeptide chains with different degrees of polymerization) measured by integrated intensity of elution pattern was comparable to the theoretical value of Suezaki and Go. Concentration dependence of the helix–coil transition temperature of (Pro‐Pro‐Gly)nwas also measured by the use of optical rotation and discussed with the theoretically

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160203

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

年代:1977

数据来源: WILEY

摘要:

AbstractInteractions between mononucleoside and dinucleoside phosphates containing adenine and/or cytosine andL‐tryptophan have been studied at low pD by proton magnetic resonance (pmr) spectroscopy. The results of those studies indicate that, despite extensive protonation of ring positions, and resulting electrostatic repulsion, ring stacking does occur between both like and unlike molecules. Geometries for stacked complexes are proposed and the extent of complex formation betweenL‐tryptophan and adenosine or cytidine in 3′ or 5′ esterified positions is discussed qualit

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160204

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

年代:1977

数据来源: WILEY

摘要:

AbstractA series of peptides, Trp‐(Pro)n‐Tyr,n= 0,…,5 were synthesized. Details of the synthetic method using the Merrifield method are given. The initial objective was to determine the characteristic distanceR0for energy transfer from tyrosine to tryptophan. This objective became submerged in the question of the structure of the chain of prolyl spacers. The efficiency of the energy transfer diminishes as the number of intervening prolines increases. Quantitatively the fit is much better if we assume that the peptides have a polyproline I structure (cis) than if we assume atranspolyproline II structure. Proton nmr spectra on the other hand suggest that then= 1,3,5 peptides are mixtures of rotamers. Our conclusions are similar to those of previous workers, i.e., that in water there is a transition from a mixture of structures for smallnto an all‐transstructure at somen>5. This means that in water, at least, proline is a dubious spacer for energy‐transfe

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160205

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe slow kinetics of annealing processes in multistranded nucleic acids is spectrophotometrically investigated using poly(A)·2poly(U) as a model system. The absorbance changes at specific wavelengths show that double‐helical (A·U) base pairs appear as transient intermediates. The annealing process is identified by the enlargement of triple‐helical sequences at the cost of (A·U) base pairs and unpaired (U) residues. A large time range in the reorganization of mismatched chain configurations is characterized by a logarithmic dependence on time. This observation is quantitatively described by a kinetic model developed by Jackson. In Jackson's model the rate‐limiting process in the slow annealing phase of maximizing triple‐helical sequences, is the removal of strand entanglements, knots, and hairpin loops by complete unwinding of those helical stretches which stabilize the mismatched configurations. The results of the present study are briefly discussed in terms of optimum conditions for hybridization experiments and for the preparation of polynucleotide complexes commonly used to produce i

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160206

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

年代:1977

数据来源: WILEY

摘要:

AbstractConformation behavior of polyethylenimine has been examined by studies of the fluorescence characteristics of derivatives of the polymer containing pyrenyl ligands. Excimer formation within the macromolecular matrix serves as a sensitive probe of group proximities. The experimental observations combined with nearest neighbor analyses lead to quantitative assessments of the extent of interaction between polymer side chains.

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160207

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

年代:1977

数据来源: WILEY

摘要:

AbstractIntensity‐fluctuation laser‐light‐scattering spectroscopy has been used to characterize the temperature dependence of the translational diffusion coefficient through the helix–coil region for the DNA isolated from bacteriophage N1. The diffusion coefficient does not change smoothly, but exhibits fine structure detail similar to that seen in the uv absorption hyperchromicity. These changes are related to the heterogeneous distribution of bases along the N1‐

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160208

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

年代:1977

数据来源: WILEY

摘要:

AbstractIntensity‐fluctuation laser‐scattering spectroscopy measurements have been reported for the DNA isolated from bacteriophage ϕ29. The cumulant method of data analysis gives well‐defined weighted average decay frequencies. Available theoretical models are shown to yield good values for the diffusion coefficient and longest intramolecular relaxation time for low‐molecular‐weight DNA's but not for higher molecular weight species. The temperature dependence of the apparent diffusion coefficient exhibits drastic oscillations in the helix–coil transition region. The number of these oscillations is consistent with independent measurements of uv hyperchromicity measurements and suggests that ϕ29‐DNA is composed of at least three regions of differin

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160209

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effects of anions of neutral salts on the fluorescence emission of six proteins as well as on tryptophan and tyrosine were studied in relation to the structure of proteins. Most anions are good quenchers of tryptophyl and tyrosyl fluorescence, free or in proteins. The results with tryptophan and tyrosine indicate involvement of a collisional quenching mechanism due to agreement with Stern–Volmer law. The deactivation of fluorescence probably occurs because of the transition from singlet state to triplet state. Lehrer's modification of Stern–Volmer law was applied to proteins. The effective quenching constants ([KQ]eff) and the fraction of fluorescence available ([fa]eff) to the quencher are also calculated.In contrast to its effect on tryptophan, CH3COO−quenches tyrosyl fluorescence and ClO4−does not. The effects on fluorescence of ribonuclease and free tyrosine are similar and without any changes in emission maximum. The anions are divided into three groups based on the effect they have on tryptophan‐containing proteins. (1) NO3−, NO2−, Br−, and I−have high [KQ]eff values and readily quench tryptophyl fluorescence of proteins causing a shift of emission maximum to a shorter wavelength. This change is due to the specific quenching of “exposed” tryptophan residues which are accessible to quenchers and the observed residual fluorescence is from the “buried” tryptophyls. (2) ClO4−and SCN−also quench fluorescence of tryptophan in proteins and have lower ([KQ]eff) values. In their presence the fluorescence maximum is shifted to a longer wavelength, which indicates the unfolding of a protein with [(fa)eff] = 1. (3) Cl−, CH3COO−, and SO4 do not have a direct effect on the fluorescence of tryptophan. Besides the “direct” effects, “indirect” effects on fluorophors in protein are also seen, pointing out that the neutral salts can interact in more than one manner with proteins. The effectiveness of anions in quenching fluorescence of proteins follows similar sequences which almost resemble the Hofmeister series, viz., SO4

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160210

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effects of varying concentrations of monovalent cation chlorides on the fluorescence of nine proteins were studied. These are discussed in terms of “direct” or “indirect” interactions with the aromatic amino acid residues. Cs+is the only cation that quenches fluorescence of proteins due to “direct” interaction with aromatic amino acid residues. Quenching is due to collisional processes. An agreement with the Stern‐Volmer relationship is shown and the values of [(KQ)eff] and [(fa)eff] are calculated. These values confirm that the fraction of fluorescence accessible to Cs+belongs to the “exposed” fluorophors. The mechanism of quenching by Cs+is due to the heavy‐atom effect because phosphorescence enhancement is also seen at the same time.The chlorides of Na+, K+, Rb+, NH4+, and Li+do not have a similar effect on the fluorescence of all proteins. For a given protein a gradation of the same effect (i.e., quenching or dequenching) is seen. Interactions with factors that “inderectly” affect fluorescence of any protein are involved and the structural features of the protein are responsible for such “indirect” effects. The results indicate that neutral salts can act in more than one manner. The changes in fluorescence are indicative of electrostatic and lyotropic effects of ions. Only electrostatic interactions which occur in the vicinity of tryptophan in proteins are reflected. Li+shows strong interactions with proteins. In 4MLiCl, BSA, papain, and trypsin show fluorescence changes that are indicative of c

ISSN:0006-3525    

DOI:10.1002/bip.1977.360160211

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

年代:1977

数据来源: WILEY