共查询到20条相似文献,搜索用时 31 毫秒
1.
Yuji Kobayashi Yukio Suezaki Katsuhiko Inouye Kaori Tanaka Kinji Kakiuchi Yoshimasa Kyogoku 《Biopolymers》1977,16(2):247-257
The properties of triple-helix formation of (Pro-Pro-Gly)n were 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)n was also measured by the use of optical rotation and discussed with the theoretically expected values. 相似文献
2.
Measurements of the molecular weight of (Pro-Pro-Gly)n and (Pro-Pro-Gly)n(Ala-Pro-Gly)m(Pro-Pro-Gly)n, which were synthesized by the solid-phase method, revealed that they formed a trimer in an aqueous solution, and dissociated into single-stranded chains on warming. Accompanying the transition, a large decrease of optical rotation was observed, like the collagen–gelatin transition. The shape of the trimeric molecule was rodlike, and the dimensions were 12 Å in diameter and 2.8 Å per residue in length, regardless of the length of Ala-Pro-Gly sequences in a peptide chain. The data indicate that both Pro-Pro-Gly sequences and Ala-Pro-Gly sequences from the triple-helical structure similar to that of collagen in aqueous solution. All optical rotational dispersion (ORD) curves of solutions of the peptides were represented by a single-term Drude equation, and the Drude constant λc was 200 nm for all peptides regardless of the length of Ala-Pro-Gly sequences. The resemblance between the helical structure formed by Pro-Pro-Gly sequences and that by Ala-Pro-Gly sequences was also suggested by the formation of the hybrid triple helix from two kinds of peptide chains with different lengths of Ala-Pro-Gly sequences. 相似文献
3.
The characterization of recently synthesized (Pro-Pro-Gly)n, n = 7, 8 is described, along with melting profile studies of its association equilibrium, and thermal quenching studies of the kinetics of its association reaction. The order of the kinetic reaction is about 3, implying that three peptide chains are involved in the activated state of the rate-limiting step. The reaction rate was found to exhibit a negative temperature coefficient. With the (Pro-Pro-Gly)7 peptide, the concentration dependence of the (Pro-Pro-Gly)n association equilibrium was observed for the first time. Detailed thermodynamic analysis for these n = 7, 8 data, together with literature data for n = 10, 15, 20 were carried out for both the simple “all-or-none” binding model and for a series of complex equilibrium models. For the latter, all of the (Pro-Pro-Gly)n data (in 10% acetic acid) are fit best with a maximally cooperative near-neighbor model with a standard enthalpy change ΔH = ?650 cal/mole of residues, and a standard entropy change ΔS = ?14.63 ?10/n cal/deg-mole of residues, wherein the ?10 eu represents an end-effect contribution to the binding free energy. With regard to optical rotatory properties and thermodynamic parameters, the data for the new n = 7, 8 peptides match rather well with the literature data for the n = 10, 15, and 20 peptides. The enthalpic stabilization per residue of the triple-helical form of (Pro-Pro-Gly)n was nearly an order of magnitude smaller than the enthalpic stabilization per additional proline obtained from direct calorimetric measurements on native collagens of different (and much lower) proline contents by Privalov and Tiktopulo. [Biopolymers (1970) 9 , 127–139.] Possible explanations for this phenomenon are discussed. 相似文献
4.
We have synthesized (Pro-Pro-βAla)n as a model for collagen. The synthetic polytripeptide, mol wt 6500, exhibits a large negative optical rotation with a very strong negative Cotton effect centered at 216 nm. The optical rotatory dispersion of (Pro-Pro-βAla)n followed a single-term Drude equation and the λc was 195 nm. The rotation decreased markedly on heating with the midpoint of the broad transition at 55°C. Preliminary studies also showed loss of structure in guadinine HCl. The circular dichroism spectrum of the polymer exhibited a deep trough at 190 nm. The marked similarities of solution properties of (Pro-Pro-βAla)n to (Pro-Pro-Gly)n suggest that β-alanine can replace glycine in generating collagen-like helix in solution. 相似文献
5.
As model peptides of collagen, (Pro-Pro-Gly)n (n = 10, 12, 14, and 15) and (Pro-Pro-Gly)n(Ala-Pro-Gly)m(Pro-Pro-Gly)n (2n + m = 15; m = 1, 3, and 5) were synthesized by the solid-phase method. The final products were pure when checked by high-voltage paper electrophoresis and by amino acid analysis. Elemental composition was also examined. 相似文献
6.
The analysis of thermal melting curves of (PPG)n (n = 10, 12, 14, and 15) and (PPG)n(APG)m (PPG)n (2n + m = 15; m = 1, 3, and 5) revealed that the enthalpy and entropy changes accompanying the transition from the random coil to the triple helix are ?2500 cal and ?6.3 e.u. per one mole of the tripeptide of the form of Pro-Pro-Gly, and ?3100 cal and ?11.2 e.u. per one mole of the tripeptide of the form of Ala-Pro-Gly. The thermal instability of the triple helix composed of Ala-Pro-Gly sequences, compared to the helix of Pro-Pro-Gly sequences, is due to the larger entropy change of Ala-Pro-Gly (?11.2 e.u.) compared to that of Pro-Pro-Gly (?6.3 e.u.), not from the difference in the enthalpy change. The difference in the enthalpy change between Pro-Pro-Gly and Ala-Pro-Gly arises from the hydrophobic bond between two pyrrolidine rings of proline residues formed in the triple helix. Since the enthalpy change for the formation of hydrophobic bonds is positive, it is also concluded that only one hydrogen bond is formed in a tripeptide unit, regardless of the amino acid sequence. The enthalpy change for the formation of this hydrogen bond is ?3100 cal/mol, and that of the hydrophobic bond between two pyrrolidine rings is +600 cal/mol. 相似文献
7.
A theoretical analysis is given of the triple-helix–random-coil transition in a mixed solution of poly(Pro-Pro-Gly)n with two different but defined degrees of polymerization n and n′. Because of the highly cooperative nature of this helix–coil transition, each polypeptide chain tends to form a triple helix with other polypeptide chains with the same degree of polymerization (size recognition). Occurrence of triple helices consisting of polypeptide chains with different degrees of polymerization (error in recognition) is studied in detail as a function of the cooperativity, and n and n′. Implication of this analysis for molecular recognition in general is discussed. 相似文献
8.
I. T. Norton D. M. Goodall K. R. J. Austen E. R. Morris D. A. Rees 《Biopolymers》1986,25(6):1009-1029
Nongelling solutions of structurally regular chain segments of agarose sulphate show disorder–order and order–disorder transitions (as monitored by the temperature dependence of optical rotation) that are closely similar to the conformational changes that accompany the sol–gel and gel–sol transitions of the unsegmented polymer. The transition midpoint temperature (Tm) for formation of the ordered structure on cooling is ~25 K lower than Tm for melting. Salt-induced conformational ordering, monitored by polarimetric stopped-flow, occurs on a millisecond time scale, and follows the dynamics expected for the process 2 coil ? helix. The equilibrium constant for helix growth (s) was calculated as a function of temperature from the calorimetric enthalpy change for helix formation (ΔHcal = ?3.0 ± 0.3 kJ per mole of disaccharide pairs in the ordered state), measured by differential scanning calorimetry. The temperature dependence of the nucleation rate constant (knuc), calculated from the observed second-order rate constant (kobs) by the relationship kobs = knuc(1 ? 1/s) gave the following activation parameters for nucleation of the ordered structure of agarose sulphate (1 mg mL?1; 0.5M Me4NCl or KCl): ΔH* = 112 ± 5 kJ mol?1; ΔS* = 262 ± 20 J mol?1 K?1; ΔG*298 = 34 ± 6 kJ mol?1; (knuc)298 = (7.5 ± 0.5) × 106 dm3 mol?1 s?1. The endpoint of the fast relaxation process corresponds to the metastable optical rotation values observed on cooling from the fully disordered form. Subsequent slow relaxation to the true equilibrium values (i.e., coincident with those observed on heating from the fully ordered state) was monitored by conventional optical rotation measurements over several weeks and follows second-order kinetics, with rate constants of (2.25 ± 0.07) × 10?4 and (3.10 ± 0.10) × 10?4 dm3 mol?1 s?1 at 293.7 and 296.2 K, respectively. This relaxation is attributed to the sequential aggregation processes helix + helix → dimer, helix + dimer → trimer, etc., with depletion of isolated helix driving the much faster coil–helix equilibrium to completion. Light-scattering measurements above and below the temperature range of the conformational transitions indicate an average aggregate size of 2–3 helices. 相似文献
9.
1. Synthetic polymers of l-prolyl-l-prolylglycine of defined chain length, (Pro-Pro-Gly)n, were found to be substrates for the enzyme protocollagen–proline hydroxylase, with optimum chain length n=5. Boiling the polymer (Pro-Pro-Gly)15 increased its activity as a substrate but had no effect on (Pro-Pro-Gly)5. 2. Protection of both or one of the N- and C-terminal groups made (Pro-Pro-Gly)3 a better substrate, and collagenase digestion of hydroxylated tert.-pentyloxy-carbonyl-(Pro-Pro-Gly)3 benzyl ester indicated that the central prolyl residues were the major points of hydroxylation. 3. The results suggest that the long-chain peptides are optimum substrates but that a triple-stranded structure is inhibitory for hydroxylation. 相似文献
10.
The polymerization kinetics and optical rotatory properties of AnBm polypeptides have been studied, where A = D ,L -Tyr, D ,L -TyrZ, D ,L -LysZ, L -AspOBzl, or L -Asp-ONBzl, and B = D ,L -GluOR (R = Me or Bzl). In most cases where An and Bm prefer the same helix sense, the polymerization of A N-carboxyanhydride (initiated by Bm in dioxane) shows first order kinetics and produces a monotonic change in optical rotation, while if opposite helix senses are preferred, the kinetics are multiphasic and the change in rotation reverses direction after the addition of several residues. The rotation change in the latter case is interpreted to mean that the helix in the A block is initially induced to take the nonpreferred sense, as originally suggested by Doty and Lundberg from similar observations on (D -GluOBzl)n-(L -GluOBzl)m. It is found here that the CD spectra for the latter polymer show the sign changes required by this hypothesis. The optical rotation curves and CD spectra for (D ,L -Tyr)n-(L -GluOBzl)20 suggest, by analogy, that (L -Tyr)n prefers the same helix sense as (L -GluOBzl)n. However, it is found that the opposite conclusion is equally consistent with the data if one considers the effects of possible changes in side-chain conformation on these data in accordance with the calculated CD spectra of Chen and Woody. The optical rotation curves for (D -GluOBzl)n-(L -GluOBzl)20, (D -Tyr)n-(L-GluOBzl)20, and (L -Tyr)n-(L -GluOBzl)20 are all found to be consistent with a two-state equilibrium model in which the A block initially takes on an induced conformation and has an increasing tendency to revert to its preferred conformation as n increases. It is concluded that in both D -Tyr and L-Tyr the side-chain and/or the backbone conformation is induced by the neighboring L -GluOBzl block, and the data do not distinguish which type of change is occurring. These results are discussed in connection with other observations bearing on the helix sense of (L -Tyr)n. 相似文献
11.
Kenji Okuyama Kaoru Okuyama Struther Arnott Motowo Takayanagi Masao Kakudo 《Journal of molecular biology》1981,152(2):427-443
(Pro-Pro-Gly)10 forms single crystals, providing X-ray diffraction data to 0.22 nm resolution. In the crystals, the polypeptides form triplexes that aggregate end-to-end in quasi-infinite helices with axial translation per tripeptide h = 0.287 nm and the corresponding rotation t = ?102.9 °. The structure, which may be an allomorph of collagen, has been refined by the linked-atom least-squares procedure. In addition, three water molecules per tripeptide have been detected by Fourier difference syntheses. One of them forms an intrachain hydrogen-bonded bridge O(Pro2) - - - W - - - O(Gly). There are also interchain hydrogen bonds (Gly)NH - - - O(Pro1) within the triplex. 相似文献
12.
Leuconostoc mesenteroides B-512FMC dextransucrase was found to synthesize dextrans of varying molecular weights by selecting the concentrations of dextransucrase and sucrose, as well as the temperature. Four enzyme concentrations (50, 10, 1.0, and 0.1 U/mL), five sucrose concentrations (20, 50, 100, 200 and 1000 mM), and two temperatures (20 °C and 30 °C) were studied. The highest amount of enzyme (50 U/mL), with the lowest concentration of sucrose (20 mM), and the lower temperature of 20 °C gave the lowest number-average molecular weight (MWn) of 20,630 Da, respectively. As the sucrose concentration was increased, 50 mM, 100 mM, and 200 mM, the MWn was 49,240 Da, 63,350 Da, and 126,720 Da, respectively. The next enzyme concentration (10 U/mL) gave a similar upward trend, starting at 73,130 Da and ending at 237,870 Da at 20 °C and 130,040 Da and ending at 415,770 Da at 30 °C. The upward trend continued for the 1.0 and 0.1 U/mL enzyme concentrations. An increase in the temperature had the overall effect of increasing the MWn for each decreasing concentration of enzyme and increasing concentration of sucrose. For 0.1 U/mL and 1000 mM sucrose at 30 °C, the MWn was 1,645,700 Da. The results of the study show that the molecular weights of the synthesized dextrans were inversely proportional to the concentration of the enzyme and directly proportional to the concentration of sucrose and the temperature. 相似文献
13.
Conformational studies of poly-L-alanine in water 总被引:5,自引:0,他引:5
The conformational properties of poly-L -alanine have been examined in aqueous solutions in order to investigate the influence of hydrophobic interactions on the helix–random coil transition. Since water is a poor solvent for poly-L -alanine, water-soluble copolymers of the type (D , L -lysine)m–(L alanine)n-(D , L -lysine)m, having 10, 160, 450, and 1000 alanyl residues, respectively, in the central block, were synthezised. The optical rotatory dispersion of the samples was investigated in the range 190–500 mμ, and the rotation at 231 mμ was related to the α-helix content, θH, of the alanine section. In salt-free solutions, at neutral pH, the three large polymers show high θH values, which are greatly reduced when the temperature is increased from 5 to 80°C. No helicity was observed for the small (n = 10) polymer. By applying the Lifson-Roig theory, the following parameters were obtained for the transition of a residue from a coil to a helical state: ν = 0.012; ΔH = ?190 ± 40 cal./mole; ΔS = ?0.55 ± 0.12 e.u. Since ΔH and ΔS differ from the values expected for a process involving only the formation of a hydrogen bond, and in a manner predicted by theories for the influence of hydrophobic bonding on helix stability, it is concluded that a hydrophobic interaction is also involved. In the presence of salt (0.2M NaCl), or when the ε-amino groups of the lysyl residues are not protonated (pH = 12), the helical form of the two large polymers (n = 450 and n = 1000) is more stable than in water. Since the electrostatic repulsion between the lysine end blocks is greatly reduced under these conditions, the alanine helical sections fold back on themselves, and this conformation is stabilized by interchain hydrophobia bonds. This structure was predicted by the theory for the equilibrium between such interacting helices, non-interacting helices, and the random coil. 相似文献
14.
The course of the reversible helix formation of poly(γ-benzyl L -glutamate) (PBG) dissolved in a mixture of dichloroacetic acid (DCA) and 1,2-dichloroethane (EDC) was followed by measuring the heat capacity and the optical rotation of the system through the transition region. The results of these measurements indicate that the transition enthalpy ΔH the transition temperature Tc, and the Zimm-Bragg parameter σ depend considerably on the PBG concentration as well as on the composition of the solvent. For the standard state of infinite dilution, however, a linear extrapolation of the measured ΔH if values results in a standard value ΔH° = 950 cal./mole, independent of the solvent composition. The results of the calorimetric measurements are discussed in relationship to changes in optical rotation. Some peculiarities in the measured thermodynamic and optical properties in solutions with relatively high content of dichloroacetic acid are reported. 相似文献
15.
The molecular mobility of calf thymus DNA molecules in solution has been discussed in terms of correlation time τ calculated from measurements of longitudinal T1 and transverse T2 magnetic relaxation times. The influence of DNA concentration and ionic strength of the solution upon freedom of movement of DNA molecules was studied for native and denatured DNA and also during thermal helix-coil transition. The dependence of τ values on temperature was carried out by comparing the values of correlation times τtat given temperature with the correlation time τ20 at 20°C. The molecular rotation of DNA at 20°C and at higher ionic strength at 0.15 and 1.0.M NaCl is described by τ values of the order of 1.0–1.2 × 10?8 and was reduced slightly with increase of temperature below the helix-coil transition. The molecular rotation of DNA in 0.02MNaCl was lower at 20°C as compared to DNA in solvents with higher NaCl concentrations and increases rapidly with increase of temperature in the range 20–60°C. The values of correlation time are characterized by fast increase at temperatures above the spectrophotometrically determined beginning of melting curve. The beginning of this increase is observed at about 65, 80, and 85°C for DNA in 0.02, 0.15, and 1.0MNaCl, respectively. Values of correlation time for denatured DNA are in all cases about 1.1–1.4 times that for native DNA. The obtained results are discussed in terms of conformation of DNA molecules in solution as well as in terms of water dipole binding in DNA hydration shells. 相似文献
16.
The optical rotatory dispersion of L -lysine oligopeptides (Lysn, n = 2–22) in solution was measured in water and in 50% methanol. A gradual change with increasing chain length in the ORD curves of the oligomers was observed at pH 4. 3. Not even a chain of 22 residues had ORD identical with that of high molecular weight poly-L -lysine. A plot of the average molar residue rotation at 233 nm versus 1/n (where n is the chain length) resulted in a straight line with an intercept of ?1900, representing the internal residue rotation of a lysine residue in the random conformation, and a slope of +6200 representing the large end effect. At pH 11.9 a stright line is obtained up to n = 12 after which it deviates from the initial slope indicating onset of helicity. Extrapolation of the initially straight line to tire higher n's provided the necessary zero-helicity values for calculation of helicity. The highest oligolysine (n = 22) showed at pH 11. 9 13% helicity, which on adding methanol to 50% increased to about 50% helicity. It is shown that helix-coil data which are usually obtained from the temperature dependence of helicity can be obtained from the dependence of helicity on chain length applying the statistical theory. For the methanol-water system the cooperativity parameter v was calculated to be in the range 0.024–0.060, with corresponding equilibrium constants w of 1.32–1.43. The helical structure was calculated to be less stable in water than in methanol-water by about 250 calories per residue. 相似文献
17.
Proton magnetic resonance of the triple helix of poly(prolylprolylglycyl)n with defined degree of polymerization 总被引:1,自引:0,他引:1
Proton magnetic resonance spectra at 220 MHz were obtained for deuterium oxide and aqueous solutions of the polytripeptides (Pro-Pro-Gly)n, which were synthesized as collagen models by the modified solid phase method. At higher temperatures, the signals of the proline Ca-protons for the peptides with n ≦ 5 and for those with n = 10 and 15 demonstrate the presence of cis and trans isomers with respect to the Gly-Pro or Pro-Pro C-N bonds. Glycine Ca-protons give typical AB type patterns. At lower temperatures, as the peptides with n = 5, 10 and 15 form triple helices, all of the resonance peaks become broad, but the whole form of the spectrum is quite similar to that of poly(l-proline) form II. The glycine Ca-proton resonances become barely detectable and the upfield peak of the two proline Ca-proton resonances fade away. At the same time, a new glycine NH resonance appears at a field slightly higher than that of a random coil. It seems to suggest that the formation of triple helices accompanies the conversion of cis proline peptide bonds into all trans bonds, and that the glycine residue environment completely changes in the helix. 相似文献
18.
de Albuquerque JE Giacomantonio C White AG Meredith P 《European biophysics journal : EBJ》2006,35(3):190-195
Photopyroelectric (PPE) spectroscopy, in the 350–1,075 nm wavelength range, was used to study the optical properties of electropolymerized
melanin films on indium tin oxide (ITO) coated glass. The PPE intensity signal as a function of the wavelength λ, V
n(λ) and its phase F
n(λ) were independently measured. Using the PPE signal intensity and the thermal and optical properties of the pyroelectric
detector, we were able to calculate the optical absorption coefficient β of melanin in the solid-state. We believe this to
be the first such measurement of its kind on this material. Additionally, we found an optical gap in these melanin films at
1.70 eV. 相似文献
19.
I L Graves 《Biopolymers》1970,9(1):11-28
The 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 × 107 cells) of (CHO)n, RNA, and DNA, respectively. The (CHO)n was 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)n with similar specific activities (radioactive counts/μg min). However, electron micrographs showed that the (CHO)n separated by using TCA had a greater variation in particle size when compared with (CHO)n separated 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)n whose synthesis was stimulated by poliovirus infection and (CHO)n from noninfected cultures, were found to be similar. When the (CHO)n was 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)n extracted with phenol. The time at which cells were pulse-labeled with 14C-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)n increased 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)n and the amounts extracted were not significantly changed. The sedimentation coefficients of RNA and (CHO)n which 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)n even 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)n reaction product(s). 相似文献
20.
Lee JM Nahm SH Kim YM Kim BD 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,108(4):619-627
Microsatellites or simple sequence repeats are highly variable DNA sequences that can be used as informative markers for the genetic analysis of plants and animals. For the development of microsatellite markers in Capsicum, microsatellites were isolated from two small-insert genomic libraries and the GenBank database. Using five types of oligonucleotides, (AT)15, (GA)15, (GT)15, (ATT)10 and (TTG)10, as probes, positive clones were isolated from the genomic libraries, and sequenced. Out of 130 positive clones, 77 clones showed microsatellite motifs, out of which 40 reliable microsatellite markers were developed. (GA)
n
and (GT)
n
sequences were found to occur most frequently in the pepper genome, followed by (TTG)
n
and (AT)
n
. Additional 36 microsatellite primers were also developed from GenBank and other published data. To measure the information content of these markers, the polymorphism information contents (PICs) were calculated. Capsicum microsatellite markers from the genomic libraries have shown a high level of PIC value, 0.76, twice the value for markers from GenBank data. Forty six microsatellite loci were placed on the SNU-RFLP linkage map, which had been derived from the interspecific cross between Capsicum annuum TF68 and Capsicum chinense Habanero. The current SNU2 pepper map with 333 markers in 15 linkage groups contains 46 SSR and 287 RFLP markers covering 1,761.5 cM with an average distance of 5.3 cM between markers.Communicated by J. Dvorak 相似文献