摘要:

The conformational feature has been studied by n.m.r. spectroscopy on the compounds, Boc‐Asn‐NHMe, Boc‐Asn‐Gly‐NHMe, Boc‐Gly‐Asn‐NHMe, and their glycosylated derivatives. From the temperature dependence of the amide proton chemical shifts and vicinal coupling constants, little change was confirmed in the peptide conformation uponN‐glycosylation. There is no particular intramolecular interaction between the peptide and carbohydrate moieties. Boc‐Asn‐Gly‐NHMe takes, to some extent, a folded structure with a hydrogen bond involving the amide proton ofN‐methylamide group. This backbone conformation is also preferable in the c

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03140.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A photoreactive derivative of the highly potent gonadotropin releasing hormone (GnRH) agonist, D‐Lys6‐GnRH(1–9)‐ethylamide, was prepared by selective modification of the e‐amino group with 2‐nitro‐4‐azidophenyl sulfenyl chloride (2,4‐NAPS C1). The modified peptide [D‐Lys(NAPS)]6‐GnRH‐(1–9)‐ethylamide was found to be a full agonist of LH release from rat pituitary cells with a relative potency 23 compared to GnRH. Covalent attachment of the photoreactive analog to rat pituitary cells resulted in prolonged activation of LH secretion whch could not be inhibited by a potent GnRH antagonist. Persistent stimulation of pituitary gonadotrophs caused by covalently bound hormone led to desensitization of

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03141.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The tripeptide, glycyl‐glycyl‐L‐valine, crystallizes as a dihydrate in the monoclinic space group P21, with a = 5.786(1), b = 7.954(2), c = 14.420(3)A, β= 93.85(2)d̀, Z = 2. The structure was solved by direct methods and refined to an R‐value of 0.040 for 876 observed reflections. The molecule exists as a zwitterion in the crystal. The peptide planes show significant deviations from planarity. The chain conformation resembles a reverse turn if the orientation of the carboxyl group is also taken into account. An intramolecular water bridge links the amino and carboxyl ends of the molecule. The crystal packing involves spatial segregation of polar and nonpolar

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03142.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Physical and structural data on two of a series of relatedN‐formyl methionine peptides are reported. The effects of peptide bondN‐methylation on chemotactic response and on conformational properties observed in solution, in the solid state and by conformational energy calculations are descri

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03143.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Crystals ofN‐formyl‐L‐methionyl‐L‐valine (C11H20N2O4S, M.W. = 276.3) are orthorhombic, space group P2 1 2121with cell constants at 294K of a = 4.851 (1), b = 14.925 (1), c = 19.745 (3) Å, V = 1429.8 (1) Å3, Z = 4 and observed (Dm) and calculated (Dx) of 1.49 and 1.488 g° cm‐3, respectively. The crystal structure was solved using automatic diffractometer data (1260 reflections ← 3s̀) and refined to a final R‐value of 0.035. This structure contains a short (2.626 (3) Å) intermolecular hydrogen bond between the carboxyl OH and theN‐acyl oxygen, a feature common to mostN‐acylamino acids andN‐acylpeptides. The peptide is nearly planar (ω= 174.6 (5)); the values of ø1, ø2, øT1and øT2are, respectively, 131.8 (4)d̀, ‐130.9 (5)d̀, ‐39.3 (4)d̀ and 142.1 (4)d̀. The methionine side chain is not zig‐zag transplanar; the side chain torsion angles are: χ11=‐60.0 (4)d̀, χ12= 176.0 (4)d̀ and χ13= 71.8 (4)d̀. The two Cγ'sfor valine have χ1‐values of ‐64.4 (5)d̀ and 173.7 (5)d̀. The formation of the parallel rather than antiparallel β‐sheet structure, the participation of the N‐formyl group in the parallel β‐sheet and the use of C‐H. O hydrogen bonds

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03144.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In a study of factors that influence the remaining secondary structure of reduced chicken eggwhite lysozyme,N‐acetyl‐D‐glucosamine (NAG) andN,N1‐diacetyl‐chitobiose (di‐NAG) were found to alter the circular dichroic (CD) spectrum of the reduced protein and its carboxymethyl derivative (Cml). Thus, negative ellipticities in the far u.v. were greater in the presence of the analogs, with NAG being the more effective. For Cml, curve fitting analysis of the CD data indicated an increased helical content in the presence of NAG by an average of 3% of the chain length, while β‐structure decreased by an equivalent amount. Other compounds structurally related to NAG produced no similar effects on the CD spectrum of Cml, nor were comparable effects of NAG in evidence on the Cm reduced derivatives of ribonuclease, chymotrypsin, wheat germ agglutinin, or α‐lactalbumin. The effect therefore appears specific between NAG and Cml. Conversion of the tryptophan residue at Position 62 of Cml to the oxindole‐alanyl derivative prevented these effects of NAG, and this residue may therefore participate in the interaction. During a 4‐day incubation at room temperature, the analog preserved the CD spectrum of Cml as well as its concentration. This effect was nearly specific when compared with other Cm reduced proteins and with other carbohydrates. Only one,N‐acetyl mannosamine, was effective in preserving the concentration of Cml, but not the CD spectrum. Since D‐glucos‐amine was entirely without effect on either the CD spectrum of Cml or on its change during incubation, the acetyl group appears essential for the NAG‐Cml interaction. The specificity between NAG and Cml is tentatively accounted for in terms of interactions with the primary structure, rather than with the remaining secondary structure. It is suggested that the stabilizing effect noted here could reflect a naturally occurring interaction betw

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03145.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Properties characteristic of the structure and function of dimeric concanavalin A have been studied as a function of pH in the acid pH range using preparations comprising intact subunits or enriched in fragmented chains. For intact subunits, the glycogen binding ability falls to zero with a midpoint at pH 4.7, the release of Mn+2, Ca+2and the fluorescent ligand 4‐methylumbelliferyl‐α‐D‐mannopyranoside from the lectin coincides over a pH range centered at pH 3.9, and the CD spectra of the aromatic amino acid residues increase sharply in amplitude between pH 4.0 and 1.5. Nevertheless, the sedimentation coefficient and peptide CD spectrum change insignificantly in the pH range 5 to 2, indicating that dimeric concanavalin A retains its secondary structure and overall hydrodynamic shape essentially unchanged upon acidification. The behavior of concanavalin comprising primarily fragmented chains is not significantly different from that of intact subunits, although it precipitates glycogen less efficiently. It is concluded that dimeric concanavalin A does not undergo a concerted change in structure upon acidification, but rather that it passes through a series of states differing from one another in their local conformations. The distinction in binding between the monosaccharide and the polysaccharide is attributed to participation of a secondary binding site in the latter case. A change in optical activity at 283 nm in the pH range 5–6 is ascribed to disruption of intersubunit interactions of Tyr 67 as the protein undergoes the dimer‐tetramer

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03146.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The highly potent cyclic analogue of α‐MSH, Ac‐[Cys4, Cys10]‐α‐MSH4–13‐NH2, was structurally modified in position 4. Four analogues were prepared and their biological activities in thein vitrofrog and lizard skin bioassays were determined. It was shown that removing the terminal acetylamino group to give [Mpa4, Cys10]‐α‐MSH4–13‐NH2resulted in little change in the biological activity, but a change in the stereochemistry of cysteine in position 4 to give Ac‐[D‐Cys4, Cys10]‐α‐MSH4–13‐NH2led to a small decrease of activity in both bioassays. Decreasing the size of the intramolecular ring by removing one methylene group to give [Maa4, Cys10]‐α‐MSH4–13‐NH2, resulted in an analogue with lower activities in both assays (about 3 times in the lizard and 500 times in the frog), and increasing the size of the ring by one methylene group to give Ac‐[Hcy4, Cys10]‐α‐MSH4–13‐NH2led to much lower activities in the lizard system and similar effects were se

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03147.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The synthesis of four biotinylated analogues of Substance P is described. The affinities of these analogues and of their complexes with avidin for the125I‐Bolton Hunter Substance P binding sites on rat brain synaptosomes were determined. While these biotinylated peptides complexed to avidin retain a good biological activity on the guinea‐pig ileum bioassay, we observe a net decrease in their binding affinities in the central nervous system. The present study confirms that in the central nervous system the higher affinity is related to theN‐terminal tetrapeptide and establishes that the free amino group (N‐α‐Arg andN‐α‐Lys) are not essential

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03148.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The Mgantigen is a well known rare mutation of the MN blood group system. The amino‐terminal pentapeptide related to human glycophorin Amg, Leu‐Ser‐Thr‐Asn‐Glu, as well as pentapeptides representing the peptide backbone of glycophorin AM, ANand AMcand other analogs, were synthesized to serve both as glycosyl transferase acceptors and as artificial antigens. These compounds were obtained by a stepwise peptide coupling strategy in

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03149.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY