ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00802.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The binding of lymphocyte function associated antigen (LFA‐1) to intercellular adhesion molecule (ICAM‐1) is responsible for several types of cellular adhesion. Amino‐acid substitution mutants of ICAM‐1 have established the importance of several sequences in this protein. We selected the binding region of Glu34for further study. One published model of domain 1 placed Glu34near the end of a β‐strand. We designed and synthesized three tripeptide derivatives centered on the Glu34sequence and attached a platform which, through hydrogen bonds, induces a rigid β‐strand conformation. Variable temperature NMR methods coupled with NOESY 2D NMR data enabled determination of the solution conformation of these compounds. ©M

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00803.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

α‐and βB2Crystallin are the major proteins in the mammalian lens. Each of these crystallins has short, flexible terminal extensions from its domain core; the two α‐crystallin subunits haveC‐terminal extensions of eight and ten amino acids whilst βB2‐crystallin hasN‐ andC‐terminal extensions of 15 and 11 amino acids, respectively. The solution conformations of these chemically synthesised extensions have been examined by two‐dimensional1H NMR spectroscopy, TheN‐terminal extension of βB2‐crystallin and theC‐terminal extensions of α‐crystallin adopt little ordered structure. In the membrane‐mimicking solvent trifluoroethanol, the α‐crystallin extensions are also unstructured. In contrast, theC‐terminal extension of βB2‐crystallin in water has a structural preference towards turn‐like structures, creating a hydrophobic region involving G198, F200 and P202. In the lens, theC‐terminal extension of βB2‐crystallin is the only one of these extensions that interacts to any large extent with other crystallins. The structural preference of theC‐terminal extension of βB2‐crystallin may therefore have implications for the role of this extension in cry

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00804.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The molecular structure of didemnin A, the parent compound of a series of antiviral cytotoxic depsipeptides extracted from a marine tunicateTrididemnum solidumof the family ofDidemnidae, has been determined by single‐crystal X‐ray diffraction. In the crystal, didemnin A molecules form pseudo‐symmetric dimeric pair. The two molecules in the dimer are held together by strong N—H…O and N—H…N hydrogen bonds. A chloride ion, placed almost symmetrically between the dimeric pair, forms N—H…Cl hydrogen bonds (3.19 and 3.23 Å) with both the molecules. The two independent molecules in the structure have closely similar geometry. For each molecule, the 23‐membered depsipeptide ring assumes a folded conformation in the shape of a ‘bent figure‐of‐eight’ similar to that observed in the didemnin B crystal structure. The major conforma‐tional differences in the macrocycle of didemnin A and didemnin B are around the Hip residue. The root mean‐square (RMS) difference of 20 of the 23 endocyclic torsion angles for the two structures is less than 10°, while the three bond torsions in the Hip residue vary by about 50°. The macrocycle conformation is stabilized by a transannular N—H…O hydrogen bond linking the isostatine amide group with the leucine carbonyl group. The truncated linear chain is folded back toward the macrocyclic ring and is held by a N—H…O hydrogen bond between the leucine amide group and Me‐Leu carbonyl group. The transannular hydrogen bond in the didemnin A structure (N4—H…O3 = 2.83 Å in both molecule a and molecule b) is noticeably stronger than that observed in the didemnin B structure (3.02 Å). The X‐ray structure of didemnin A is generally consistent with that obtained by NMR studies. Within the crystal, the molecules are packed in zig‐zag chains formed by intermolecular O— H…O hydrogen bonds. The crystal structure and packing of didemnin A are quite different

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00805.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Pepsin successfully catalyzed the synthesis of several hydrophobic octa‐ and decapeptides in dimethylformamide‐water solutions containing concentrated urea at pH 4.65. The factors that influence peptide synthesis in the presence of urea aere studied using condensation of the tripeptides Z‐Ala‐Ala‐Phe‐OH and H‐Leu‐Ala‐Ala‐OCH3as a model. The dependence of Z‐Ala‐Ala‐Phe‐Leu‐Ala‐Ala‐OCH3yield on pepsin concentration and pH, as well as the behavior of pepsin during peptide synthesis were studied. It was shown that pepsin catalyzed the synthesis of Z‐Ala‐Ala‐Phe‐Leu‐Ala‐Ala‐OCH3in guanidine hydro‐chloride and sodium dodecyl sulfate solutions. Other proteinases, subtilisin and thermolysin, were applied for the synthesis ofp‐nitroanilides of tri‐ and tetrapeptides in urea solutions.Proteinase‐catalyzed peptide synthesis in the presence of denaturing agents might help to overcome the limitations caused by poor solubility of the starting peptide derivatives, although this effect is sometimes coun

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00806.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Aggregation due to hydrogen‐bonded interchain association is thought to be the cause of difficult sequences in solid‐phase peptide synthesis. Hmb (2‐hydroxy‐4‐methoxybenzyl) was introduced recently as a backbone‐protecting group for Fmoc/tBu strategies which inhibits this association. Hmb derivatives of four amino acids are now available commercially. This paper describes the syntheses of two difficult sequences which were achieved by judicious use of the Hmb protecting group. (Hmb)Gly. which is attractive because of the ease of coupling the following residue, did not always produce the expected long‐range effect. Moving the Hmb protection to a suitable preceding position in the sequence overcame this shortcoming. ©M

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00807.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The neuroexcitotoxic nonprotein amino acid, β‐N‐oxalo‐L‐α, β‐diaminopropionic acid (β‐N‐ODAP) was found in Panax species such as Panax ginseng C.A. Meyer’(cultivated in Northeastern China),Panax quinquefolius(L), Panax notoginseng ‘F.H. Chen’(cultivated in Southwestern China), Korean red ginseng and Jilin (China) red ginseng. β‐N‐ODAP was verified to be a natural substance, and its isomer α‐N‐oxalo‐L‐α, β‐diaminopropionic acid (α‐N‐ODAP) is very likely an artifact generated during the separation process. The interconversion between β‐N‐ODAP and α‐N‐ODAP was observed. Results showed that both β‐N‐ODAP and α‐N‐ODAP can easily be converted into their isomers at higher temperature or in acidic and basic solution. Their interconversion equilibrium constant and rate constants were obtained. Upon extensive study and a good understanding of the interconversion, accurate physical constants and spectroscopic dat

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00808.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

High‐throughput analysis for purity and molecular weight determination of synthetic peptides including characterisation of any peptidic byproducts arising from synthesis is described. The data from electrospray mass spectrometry are processed with an algorithm that calculates the contribution of the target peptide and each of the identifiable contaminants to the total ionizable material in a sample of synthetic peptide. All essential data are obtained by one instrumental technique in<3 min per sample. The technique has distinct advantages in the rapid analysis of the many hundreds of peptides/peptidomimetics required in systematic quantitative structure‐activity relationship and other investigations. ©Munksgaard

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00809.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Fluorogenic substrates for chymosin [Dns‐Leu‐Ser‐Phe‐Trp‐Ala‐Leu‐OCH2Py (I), Dns‐Leu‐Ser‐Phe‐Met‐Trp‐Leu‐OCH2Py (II), Dns‐Leu‐Ser‐Leu‐Trp‐Ala‐Leu‐OCH2Py (III), Dns‐Leu‐Ala‐Phe‐Trp‐Ala‐Leu‐OCH2Py (IV), Dns‐Leu‐Ser‐Phe‐Leu‐Ala‐Leu‐OCH2Py (V) and Dns‐Leu‐Ser‐Phe‐Phe‐Ala‐Leu‐OCH2Py (VI)] were synthesized by a solution method. The obtained substrates I‐VI were cleaved specifically (between the Phe and Trp residues for substrates I and IV, the Phe and Met residues for substrate II, the Leu and Trp residues for substrate III, the Phe and Leu residues for substrate V, and the Phe and Phe residues for substrate VI) by chymosin. The fluorescence of substrates I‐IV (345 nm) increased with their hydrolysis, and hydrolysis rates were obtained by measuring the increase in fluorescence. The minimum detectable chymosin concentrations for substrates I and IV were about 1 nM; those for substrates II and III were about 4 and 2 nM. This assay method is very sensitive, and it is possible to determine the chymosin activity rapidly and easily. Substrates I and IV‐VI were hydrolyzed by chymosin two times faster than substrates II and III. The effect of the am

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00810.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Gelsolin and thymosin β4 appear to be two important actin‐associated proteins involved in the regulation of actin polymerization. It has been widely demonstrated that thymosin is the major cellular actin‐sequestering factor shifting the polymerization equilibriuni of actin towards a monomeric state. At the same time gelsolin, a Ca2+and inositol phosphate sensitive protein, regulates actin filament length. The interactions of these two proteins with actin are rather complex and require the participation of several complementary peptide sequences. We have identified a common motif, (I. V)EKFD, in the two proteins in the functional sequences so far examined. Gelsolin‐ and thymosin β4‐related peptides including the common motif were synthesized and their structural and functional properties studied. These two sequences exert a major inhibitory effect on salt‐induced actin polymerization. We used circular dichroism and Fourier‐transform infrared spectroscopy to show that the two synthetic peptides present some secondary structure in solution. As far as the peptide derived from the thymosin sequence was concerned, α‐helical structure was induced by trifluoroethanol as observed with the full‐length molecule. These experiments underscore the importance of the conformational state of peptide fragments in their biological activities. ELISA and fluorescence measurements have been used to identify the binding regions of these fragments to aC‐terminal region (subdomain 1) of the actin sequence. Our results also emphasize the relationship between the propensity of small sequences to form secondary structures and their propensity for biological activity as related to actin interaction and inhibition of actin polymerizati

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1996.tb00811.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY