Peptides In Terms Research Articles

Optimal sequences for non-phosphate-directed phosphorylation by protein kinase CK1 (casein kinase-1)--a re-evaluation.

A variety of synthetic peptides derived from either the inhibitor-2 (I-2) phosphoacceptor sites or the optimal sequences selected in an oriented peptide library have been compared for their susceptibility to phosphorylation by protein kinase CK1 (also termed casein kinase-1). The I-2-derived peptides are by far preferred over the library peptides by both rat liver CK1 (and by the alpha/beta, gamma and delta/epsilon isoforms immunoprecipitated from it) and recombinant Xenopus laevis CK1 alpha. The superiority of the I-2-derived peptides over the library ones is reflected by Vmax values one to two orders of magnitude higher while the Km values are comparable. Individual substitutions of any of the aspartic acids with alanine in the I-2-derived peptide RRKHAAIGDDDDAYSITA is detrimental, producing both a fall in Vmax and an increase in Km which are more pronounced at position n -3, but also quite significant at positions n -4, n -5 and, to a lesser extent, n -6. The unfavourable effect of these substitutions is more evident with rat liver CK1 than with recombinant Xenopus laevis CK1 alpha. The chimeric peptide IGDDDDAY-S-IIIFFA, resulting from the combination of the N-terminal acidic sequence of the I-2 (Ser86) site and the C-terminal hydrophobic cluster selected in the library peptides (MAEFDTG-S-IIIFFAKKK and MAYYDAA-S-IIIFFAKKK) is phosphorylated as efficiently as the I-2-derived peptide in terms of both Km and Vmax. These combined data strongly support the conclusion that, at variance with the optimal sequences selected in the library, optimal non-phosphate-directed phosphorylation of peptide substrates by CK1 critically relies on the presence of a cluster of acidic residues (preferably aspartic acid) upstream from position n -2, while the highly hydrophobic region downstream from serine selected in the library appears to be dispensable. The reason for these discrepancies remains unclear. The possibility that the library data are biased by the invariant elements forming its scaffold (MA-x-x-x-x-x-SI-x-x-x-x-AKKK) would be consistent with the observation that the library-selected peptides, despite their low Km values, fail to compete against the phosphorylation of protein and peptide substrates by CK1, suggesting that they bind to elements partially distinct from those responsible for substrate recognition.

Design and synthesis of potent tyr(OMe)5-gonadotropin-releasing hormone (GnRH) analogues with modifications at positions 6, 9 and 10

We have recently reported the synthesis and the conformational properties of some Gonadotropin-releasing hormone (GnRH) analogues in which the tyrosine residue at position 5 is substituted with tyrosine-O-methyl (Keramida et al., Let. Pept. Sci., 3 (1996) 257/Matsoukas et al., Eur. J. Med. Chem., 32 (1997) 927). The analogue [Tyr-(OMe)5]-GnRH was found to exert a lower degree of desensitization than the native GnRH peptides in terms of pituitary gonadotropin (GTH) release in goldfish. Compared to GnRH, however, [Tyr-(OMe)5]-GnRH exerted a lower GTH-release potency in cultured goldfish pituitary fragments, and was bound with a lower binding affinity to the rat pituitary GnRH receptors. In order to increase the potency of [Tyr-(OMe)5]-GnRH, we have synthesized a group of GnRH peptides containing Tyr-(OMe)5 in combination with other substitutions at positions 6, 9 and 10 and we have estimated their binding affinity for the rat pituitary receptors and gonadotropin (GTH) release potency in the goldfish pituitary. A selected number of these analogues was also tested for their ability to induce ovulation in seabass. The important structural modifications that increased the binding and gonadotropic activity of [Tyr(OMe)5]-GnRH in vitro and in vivo were found to include the replacement of the proline at position 9 with azetidine, glycine amide terminus with an alkyl amide group and Gly6 residue with hydrophilicd-amino acids such asd-Arg6. Overall, the findings provide SAR information on a group of novel GnRH peptides that can be also used to induce ovulation in teleosts.

Early Osteoblast Attachment, Spreading, and Focal Adhesions on RGD Coated Surfaces

AbstractCells recognize and interact with the extracellular matrix (ECM) through heterodimeric receptors known as integrins. The objective of our work is to immobilize integrin-stimulating peptides to bone-contacting implants in order to control cellular activity and response.We have previously demonstrated that cysteine (C) containing peptides self-assemble onto gold-coated substrates. Investigations have focused on the RGD (Arg-Gly-Asp) peptide sequence since it is found in several bone ECM proteins. Gold was first coated onto glass coverslips by evaporation and the peptide was applied in a 0.22 mM solution. Contact angle and surface plasmon resonance verified RGDC peptide attachment and formation of a monolayer.Rat calvarial osteoblasts isolated from six-day-old rat pups were used from passages one to three. Cell attachment at 20 minutes is 100% greater on RGDC than on CG (control peptides) or plain gold surfaces. Cells on RGDC also stain positively for vinculin, a protein which is present in focal adhesions (functional structures into which integrins assemble) whereas surfaces without integrin stimulating peptides do not. Scanning electron micrographs show cells to be more spread and have more processes at 20 minutes, 1, 3, and 24 hours on RGDC. Live video images of these surfaces from zero to three hours after plating confirmed earlier and greater cell spreading on RGDC.Ongoingin vitroexperiments are investigating the long-term response of osteoblasts to RGDC and other immobilized peptides in terms of differentiation, matrix production, and integrin expression.

Chapter 6 Circadian rhythms of neuropeptides in the suprachiasmatic nucleus

Publisher Summary The suprachiasmatic nucleus (SCN) in the mammalian brain, the locus of the circadian pacemaker, contains a variety of neuropeptides acting as neurotransmitters or modulators. Levels of four peptides that are synthesized in the SCN were determined throughout the 24-hour period. Time course analysis of message abundance encoding these peptides suggested that the changes of message levels underlie these circadian profiles of peptide contents in the SCN. Vasopressin and somatostatin messenger RNA (mRNA) levels were found to exhibit a circadian rhythm in the SCN under constant conditions, while the mRNA content encoding vasoactive intestinal polypeptide (VIP) did not show such a rhythm. The presence of two distinct subtypes of peptides in terms of circadian profiles of their contents, in morphologically distinct subregions, is another indication that the substructure of the SCN is involved in the proper maintenance of the circadian rhythm. One of the remarkable observations in the present series of experiments is the presence or absence of different circadian variations in distinct subdivisions of the SCN, shown by various neurochemical substances. Activity against vasopressin (AVP) and somatostatin (SS) displayed circadian rhythms with similar profiles, whereas VIP and gastrin releasing peptide (GRP) did not change unless the environmental lighting conditions changed. Time courses of mRNA levels, in general, showed a parallel change to corresponding peptides with some phase differences.

Design and synthesis of amphiphilic alpha-helical model peptides with systematically varied hydrophobic-hydrophilic balance and their interaction with lipid- and bio-membranes.

Five amphiphilic alpha-helical peptides of 18 residues containing a hydrophobic Trp residue as a fluorescence probe were designed. The peptides were made up of hydrophobic Leu and hydrophilic Lys residues of a ratio of 13:5, 11:7, 9:9, 7:11, and 5:13 (abbreviated as Hels 13-5, 11-7, 9-9, 7-11, and 5-13, respectively). These peptides generate ideal amphiphilic alpha-helical structures, which have systematically varied hydrophobic-hydrophilic balance (relative amphiphilic potential) as a result of different hydrophobicities and almost the same hydrophobic moments. Their hydrophobic-hydrophilic balance was estimated both theoretically from the calculated hydrophobicity values (or the magnitude of hydrophobic faces) and experimentally from the retention times in reverse phase high-performance liquid chromatography (RP-HPLC). Circular dichroism, liposome-lytic, and Trp-fluorescent studies in buffer and in the presence of acidic and neutral liposomes clearly showed that the increasing hydrophobic face area not only increases the affinity for lipid but also increases the trend of self-association. The structure-activity relationship estimated by means of leakage ability and hemolytic activity demonstrated that the model- and bio-membrane perturbation ability is completely parallel to the magnitude of the hydrophobic face area. The lipid-binding study in guanidine hydrochloride solution showed that the peptides with a hydrophobic face larger than the hydrophilic face (Hels 13-5 and 11-7) immerse their hydrophobic regions in lipid bilayers and that the inverse ones (Hels 7-11 and 5-13) interact only between the anionic lipid head groups and cationic peptide residues on liposome surfaces. The peptide Hel 9-9, which has exactly the same hydrophobic and hydrophilic regions, was found to be at a critical boundary among these peptides in terms of (1) behavior of peptide self-aggregation in buffer solution and membrane perturbation ability, (2) transfer from bulk solution to neutral lipid bilayers, and (3) necessity of charge interaction in lipid-peptide binding.

Induction of CTL in vivo by major histocompatibility complex class I‐peptide complexes covalently associated on the cell surface

The identification of endogenously produced antigenic peptides presented by MHC class I molecules has opened the way to peptide-based strategies for CTL induction in vivo. Here we demonstrate that the induction in vivo of CTL directed against naturally processed antigens can be triggered by injection of syngeneic cells expressing covalent major histocompatibility complex class I-peptide complexes. In the model system used, the induction of HLA-Cw3 specific cytotoxic T lymphocytes (CTL) in mice by cell surface-associated, covalent H-2Kd (Kd)-Cw3 peptide complexes was investigated. The Kd-restricted Cw3 peptide 170-179 (RYLKNGKETL), which mimics the major natural epitope recognized by Cw3-specific CTL in H-2d mice, was converted to a photoreactive derivative by replacing Arg-170 with N-beta-(4-azidosalicyloyl)-L-2,3-diaminopropionic acid. This peptide derivative was equivalent to the parental Cw3 peptide in terms of binding to Kd molecules and recognition by Cw3-specific CTL clones and could be cross-linked efficiently and selectively to Kd molecules on the surface of Con A-stimulated spleen cells from H-2d mice. Photocross-linking prevented the rapid dissociation of Kd-peptide derivative complexes that takes place under physiological conditions. Cultures of spleen cells or peritoneal exudate cells from mice inoculated i.p. with peptide-pulsed and photocross-linked cells developed a strong CTL response following antigenic stimulation in vitro. The cultured cells efficiently lysed not only target cells sensitized with the Cw3 170-179 peptide but also target cells transfected with the Cw3 gene. Moreover, their TCR preferentially expressed V beta 10 and J alpha pHDS58 segments as well as conserved junctional sequences, as has been observed previously in Cw3-specific CTL responses. In contrast, no Cw3-specific CTL response could be obtained in cultures derived from mice injected with Con A-stimulated spleen cells pulsed with the peptide derivative without photocross-linking.

Preformed purified peptide/major histocompatibility class I complexes are potent stimulators of class I‐restricted T cell hybridomas

A panel of antigen-specific, major histocompatibility complex class I-restricted T cell hybridomas has been generated to examine the capacity of peptide/class I complexes to stimulate T cells at the molecular level. Peptide/class I complexes were generated in detergent solution, purified and quantitated. Latex particles were subsequently coated with known amounts of preformed complexes and used to stimulate the T cell hybridomas. Stimulation was specific, i.e. only the appropriate peptide/class I combination were stimulatory, and quite sensitive, i.e. as little as 300 complexes per bead could be detected by the T cells. Preformed complexes were about 500,000 times more potent than free peptide in terms of T cell stimulation, demonstrating the physiological relevancy of the biochemically generated complexes. Surprisingly, the majority (including the most sensitive of the hybridomas) had lost CD8 expression, suggesting that antigen-specific stimulation of class I-restricted T cell hybridomas, as assessed by IL-2 release, does not depend on CD8.

Insulin-like Growth Factor-I in the Ovary of the Laying Hen: Gene Expression and Biological Actions on Granulosa and Thecal Cells

Concentrations of insulin-like growth factor-I (IGF-I) were measured in granulosa and thecal tissue dissected from the three largest follicles in the ovaries of laying hens. The higher concentration was found in extracts of granulosa (0.82 ± 0.01 pmol/g wet wt) and theca (0.36 ± 0.02), both of which were greater than that in liver extracts (0.25 ± 0.01). RNA was extracted from these tissues, and by using reverse transcription and the polymerase chain reaction with primers specific for chicken IGF-I, both granulosa and thecal tissue were shown to express chicken IGF-I mRNA. Granulosa and thecal cell cultures were established and used to measure IGF binding sites and the response to exogenous IGF peptides in terms of DNA synthesis. Both cell types bound [ 125I]IGF-I, which was displaced by IGF-I, IGF-II, and insulin in descending order of potency, characteristic of a type-I IGF receptor. Treatment of granulosa and thecal cell cultures with IGF-I resulted in a dose-dependent increase in [ 3H]thymidine incorporation into DNA by both cell types. LH, but not FSH, stimulated DNA synthesis in cultured granulosa cells but not in cultured thecal cells. This effect was enhanced in granulosa cells by the addition of IGF-I to the culture medium. These data are consistent with an autocrine or paracrine role for IGF-I within the developing ovarian follicle of the domestic hen.

Human immune responses to the Plasmodium falciparum ring-infected erythrocyte surface antigen (Pf155/RESA) after a decrease in malaria transmission in Madagascar.

A resurgence of falciparum malaria occurred in the central highlands of Madagascar in the 1980s and was responsible for an outbreak in 1986-1987. Since 1989, transmission has decreased dramatically. In April 1991, we investigated the humoral and cellular immune responses of 53 inhabitants of the village of Manarintsoa to six synthetic peptides that reproduced the major B and/or T cell epitopes of the Pfl 55/ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum. The presence of RESA peptide-reactive T cells was assessed by lymphocyte proliferation assay as well as by detection of in vitro production of interferon-gamma and interleukin-2. The mean values of these cellular responses were low, and the results obtained in these three tests showed no correlation. Twenty-seven subjects presented with anti-RESA antibodies as detected by modified immunofluorescent assay, but the mean levels of anti-peptide antibodies were low. When compared with data obtained in January 1988 from the same subjects with three of the six peptides, the present data demonstrated a decrease in the response to these peptides in terms of both proliferative response and mean antibody titers. The mean values of anti-RESA antibodies remained unchanged. The fact that cellular and humoral responses to the major Pfl 55/RESA epitopes decreased but did not disappear probably reflects both the remainder of the acquired immunity resulting from the 1986-1987 malaria outbreak, and its conservation by the very low level of transmission since 1989.

Characterisation of a tryptic peptide from human placental ribonuclease inhibitor which inhibits ribonuclease activity.

Affinity-purified human placental ribonuclease inhibitor (PRI) was digested by trypsin. Subsequent fractionation of the hydrolysate by HPLC yielded 44 fractions, 3 of which retained the ability to inhibit ribonuclease. One of these, the most active, was a 15 amino acid peptide which had an amino acid composition corresponding to a tryptic fragment of PRI. This peptide was synthesised, and preliminary experiments were carried out on its interactions with ribonuclease. These experiments suggested that the behaviour of the peptide in terms of effect of pH, and effect of salt concentration were similar to the protein from which it was derived. These studies together with the strategic positioning of the peptide in the sequence of the ribonuclease inhibitor, suggest that this segment of PRI has an important role in the inhibitory activity of the intact protein.

The effect of orientation of epitopes on the immunogenicity of chimeric synthetic peptides representing measles virus protein sequences

We have studied the influence of the orientation of T- and B-cell epitopes on the immunogenicity of chimeric synthetic peptides in terms of the ability of the T-cell epitope to provide help for the production of antibody to the B-cell epitope. A T-cell epitope from the fusion protein of measles virus (288–302), previously shown to act as a T-helper epitope in a panel of six inbred mouse strains, was co-linearly synthesized at either the amino- or carboxyl- terminus of a B-cell epitope from the haemagglutinin of the virus (188–199) with or without the inclusion of a glycine-glycine spacer. The four chimeric peptides were used to immunize a panel of five mouse strains and induced good anti-chimera antibody responses. In general, the chimeras in which the T-cell epitope was amino-terminal to the B-cell epitope induced antibodies which bound well to the B-cell epitope whereas the carboxyl-terminal orientation of the T-cell epitope with respect to the B-cell epitope failed to induce such antibody. These latter chimeras induced the production of antibodies which preferentially bound to the T-cell epitope. The inclusion of the gly-gly spacer in the chimeras did not enhance their immunogenicity nor did it increase antibody titres to the B-cell epitope. The affinity of the anti-peptide antibodies was markedly influenced by the orientation of the epitopes in the chimeras. The antibody elicited by the peptide in which the T-cell epitope was amino terminal to the B-cell epitope had significantly higher affinity for the B-cell epitope than that induced by immunization with the peptide in the reverse orientation.

Beta-adrenergic and peptide N-terminal histidine and C-terminal isoleucine stimulation of N-acetyl-transferase activity and melatonin production in the cultured rat pineal gland.

The purpose of this investigation was to compare the effect of peptide N-terminal histidine and C-terminal isoleucine (PHI) with that of the beta-adrenergic agonist isoproterenol (ISO) on N-acetyltransferase (NAT) activity and melatonin production in the cultured rat pineal gland. Pineal glands were removed and placed in organ culture containing PHI, ISO, or PHI plus ISO at different dosages, and subsequent changes in NAT activity and melatonin levels were measured. PHI stimulated these parameters in both a time- and dose-dependent manner. Combined treatment with PHI (10(-6) M) and high doses of ISO (either 10(-7) or 10(-8) M) did not potentiate the effect of the peptide in terms of either NAT activity or melatonin levels in the pineal gland. However, at a lower concentration, ISO (10(-9) M) had additive effects to those of PHI in both cultured pineals and medium. The results suggest that PHI modulates melatonin synthesis in the rat pineal gland. Furthermore, stimulation of the pineal with both PHI and ISO demonstrates an additive effect rather than a synergistic action of these compounds. It is presumed that ISO and PHI stimulate pineal melatonin production via separate receptors, but they probably use the same intracellular second messenger, cAMP, to do so. This is the first study showing an effect of the peptide PHI on pineal melatonin production in any vertebrate.

Stimulation of autocrine platelet- derived growth factor AA-homodimer and transforming growth factor β in vascular smooth muscle cells

We have investigated the interrelationship between growth factors and vasoconstrictor peptides in terms of their possible paracrine/autocrine regulation of vascular smooth muscle cell differentiation/proliferation. Responses of quiescent cells from spontaneously hypertensive and Wistar-Kyoto rats to stimulation with a selected number of growth factors- and vasoconstrictor peptides were established (induction of mRNA as well as secretion of immunoreactive peptides). A single exposure of quiescent vascular smooth muscle cells to the vasoconstrictor peptides Angiotensin II and Endothelin-1 (10 −8 M each) resulted in a prolonged induction of platelet- derived growth factor A-chain and transforming growth factor β transcripts (maximal at 5–6 hrs poststimulatory). The interrelationship between platelet- derived growth factor AA and transforming growth factor β was investigated in experiments using the pure peptides individually for stimulation of mRNA and peptide secretion. Both growth factors enhanced their own and one anothers transcript expression. The results demonstrated that in spontaneously hypertensive rats, an established animal model of hypertension, the steady state balance of this set of growth factors may be disturbed. Defects involved may be attributable to alterations in the secretory machinery and/or amount of autocrine growth factor produced.

Enkephalin hydrolysis by human serum biotinidase

Purified human serum biotinidase exhibited amino-exo-peptidase activity. Enkephalins and dynorphin A (less than 10-mer) seemed to be the most appropriate substrates among various physiological peptides in terms of the k cat/ K m values. Similar k cat/ K m values were obtained for both biocytin (biotinyllysine) and these opioid-neuropeptides. Neuro-oligo-peptides ranging from 2-mer to 18-mer were hydrolyzed. The presence of amino group at the carboxyl terminal position increased the k cat/ K m value by decreasing the K m value. The results of inhibition studies using various kinds of antibiotic inhibitors, metals, and chelating agents indicated that enkephalin hydrolysis was mediated by the peptide-hydrolyzing center probably containing Zn ions. This aminopeptidase activity was uniquely inhibited by a vitamin of biocytin. The reason for the high content of biotinidase activity in serum may be related to the binary function of this enzyme; i.e., biocytin hydrolyzing amidase and enkephalin hydrolyzing aminopeptidase functions.

The α subunit of human chorionic gonadotropin hormone synthesized in insect cells using a baculovirus vector is biologically active

A recombinant baculovirus, vAcα hCG, having a replacement of the viral polyhedrin gene with the cDNA encoding the α subunit of hCG was used to express αhCH, an extensively glycosylated hormone in insect cells. Virus-infected cells, 72 h pi, secreted ∼ 11.3 μg αhCG/2 × 10 4 cells/ml which was identical to the native hormonal peptide in terms of electrophoretic mobility, immunoreactivity and bioactivity on association with β subunit, as evident by its binding to rat testicular cells and induction of steroidogenesis in a mouse Leydig cell bioassay system. The αhCG secreted into the medium represented ∼20–30% of the total hCG synthesized by vAcα CG infected insect cells. The implications of using a very late promoter, in a baculovirus expression system, for directing the transcription of a gene whose gene product requires extensive post-translation modifications are discussed.

Comparison of the effects of endothelin-1 and endothelin-3 on the rat stomach

The effects of systemic administration of endothelin-1 and endothelin-3 on the susceptibility of the stomach to injury were compared in the anesthetized rat, as were their effects on gastric vascular tone, systemic blood pressure and hematocrit. When infused at concentrations in the 10 −7–10 −6 M range, endothelin-1 was a far more potent hypertensive agent than endothelin-3. Endothelin-1 caused significant hemoconcentration, while endothelin-3 did not. Endothelin-1 was approximately 5- to 10-times more potent as a vasoconstrictor in the stomach and a similar difference in potencies was observed when the ability of these peptides to increase the susceptibility of the stomach to ethanol-induced damage was compared. The two peptides were equipotent in producing gastric mucosal hemorrhage in the absence of any exogenous irritant. These results demonstrate that like endothelin-1, endothelin-3 has ulcerogenic and vasoconstriction actions in the stomach. While there are very large differences in the potencies of the two peptides in terms of producing systemic hypertension and hemoconcentration, the differences in the potency of the gastric ulcerogenic and vasoconstrictor effects are much less marked.

Zinc Complexation in the Phloem of Blight-affected Citrus

Abstract Extracts from Zn-accumulating phloem tissue of blight-affected trees had higher Zn-binding capacity than extracts from healthy trees. A 4-kDa, highly anionic, zinc-binding fraction was isolated from the phloem of predecline and decline stage ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] and ‘Marsh’ grapefruit (C. paradisi Macf.) trees grown on blight-susceptible rootstocks. Diethylaminoethyl (DEAE) Sephadex chromatography revealed the Zn-binding fraction contained at least four different anionic species. Two of the four species were present in healthy as well as predecline- and decline-stage trees. The other two species were found in only the predecline and decline trees. All Zn-binding factors were similar to the poly(γ-glutamyl-cysteinyl) glycine peptides in terms of size, anionic character, pH and temperature stability, capacity to bind other metals, and spectrophotometric properties.

Human T hybridoma-derived immunoglobulin-binding factors.

A human T hybridoma was generated lacking demonstrable low-affinity IgE surface receptors. This cell line produces spontaneously immunoglobulin-binding factors. The factors have an affinity for human IgE and IgG as well as for IgG from other species. The binding factors were purified by concanavalin A affinity chromatography, an IgE immunoaffinity column and SDS-PAGE. This purification procedure resulted in five major proteins bands at 13, 15, 30, 60 and less than 150 kilodaltons. As judged by Western blot analysis, all bands were variably glycosylated and were capable of binding IgE. Biological activity resided even within the small molecular weight (13 kilodaltons) peptide in terms of inhibiting IgE synthesis of the U266 B cell line and net IgE synthesis of B cells from atopic blood donors. Additionally, semipurified binding factor preparations also inhibited the Pokeweed mitogen-induced IgG synthesis while stimulating IgE synthesis at the same time. At present it is not clear whether the different molecular entities are dimers or polymers of the same protein, or are all derived from one larger protein (proteolytically cleaved), or whether they are completely different peptides mediating similar immunoglobulin-binding capacities as well as similar biological activities. Glycosylation of binding factors is not responsible for binding to immunoglobulins, but might be important for its biological activity.

A graphics display-oriented strategy for the amino acid sequencing of peptides by tandem mass spectrometry

A graphics display-oriented method for the computer-aided interpretation of the mass spectrum of a peptide in terms of its amino acid sequence is presented. The spectrum is obtained by collision induced decomposition of the protonated molecular ion (M+H)+ of the peptide generated by fast atom bombardment in the first double focussing mass analyzer of a tandem mass spectrometer and the product ion mass spectrum (CID spectrum) recorded by the second double focussing mass analyzer. The algorithm displays all series of peaks differing by the mass of -NH-CHR-CO- for the various amino acids. This display, which is very fast and can be augmented through interrogation by the user, greatly facilitates the determination of the amino acid sequence. The method is demonstrated on the spectra of a undecapeptide of (M+H)+ m/z = 1208.2 and a tetradecapeptide of (M+H)+ m/z = 1758.9.

Dynamics and conformational energetics of a peptide hormone: vasopressin.

A theoretical methodology for use in conjunction with experiment was applied to the neurohypophyseal hormone lysine vasopressin for elucidation of its accessible molecular conformations and associated flexibility, conformational transitions, and dynamics. Molecular dynamics and energy minimization techniques make possible a description of the conformational properties of a peptide in terms of the precise positions of atoms, their fluctuations in time, and the interatomic forces acting on them. Analysis of the dynamic trajectory of lysine vasopressin shows the ability of a flexible peptide hormone to undergo spontaneous conformational transitions. The excursions of an individual phenylalanine residue exemplify the dynamic flexibility and multiple conformational states available to small peptide hormones and their component residues, even within constraints imposed by a cyclic hexapeptide ring.