bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, biological activity and conformational analysis of cyclic GRF analogs
Authors: FELIX ARTHUR M. , HEIMER EDGAR P. , WANG CHING‐TSO , LAMBROS THEODORE J. , FOURNIER ALAIN , MOWLES THOMAS F. , MAINES SARAH , CAMPBELL ROBERT M. , WEGRZYNSKI BOGDA B. , TOOME VOLDEMAR , FRY DAVID , MADISON VINCENT S.
Published: August 2010

A novel cyclic GRF analog, cyclo(Asp8‐Lys12)‐[Asp8,Ala15]‐GRF(1‐29)‐NH2, i.e. cyclo8.12[Asp8,Ala15]‐GRF(1‐29)‐NH2, was synthesized by the solid phase procedure and found to retain significant biological activity. Solid phase cyclization of Asp8 to Lys12 proceeded rapidly (∼2h) using the BOP reagent. Substitution of Ala12 with d‐Ala2 and/or NH2‐terminal replacement (desNH2‐Tyr1 or N‐MeTyr1) in the cyclo8.12[Asp8,Ala15]‐GRF(1‐29)‐NH2 system resulted in highly potent analogs that were also active in vivo. Conformational analysis (circular dichroism and molecular dynamics calculations based on NOE‐derived distance constraints) demonstrated that cyclo8.12[Asp8,Ala15]‐GRF(1‐29)‐NH2 contains a long α‐helical segment even in aqueous solution. A series of cyclo8.12 stereoisomers containing d‐Asp8 and/or d‐Lys12 were prepared and also found to be highly potent and to retain significant α‐helical conformation. The high biological activity of cyclo8.12[N‐MeTyr1,d‐Ala2,Asp8,Ala15]‐GRF(1‐29)‐NH2 may be explained on the basis of retention of a preferred bioactive conformation.
Novel linear antagonists of the antidiuretic (V2) and vasopressor (V1) responses to vasopressin
Authors: MANNING M. , KLIS W.A. , KRUSZYNSKI M. , PRZYBYLSKI J.P. , OLMA A. , WO N.C. , PELTON G.H. , SAWYER W.H.
Published: August 2010

We report the solid phase synthesis of a series of 16 linear analogues of the cyclic antagonist of the antidiuretic (V2) and the vasopressor (V1) responses to arginine vasopressin (AVP), d(CH2)5[d‐Tyr(Et)2,Val4]AVP (A). Peptide 1, the linear precursor of (A), (CH2)5(SH)‐CH2‐CO‐d‐Tyr(Et)‐Phe‐Val‐Asn‐Cys‐Pro‐Arg‐Gly‐NH2 was modified at position six with α‐L‐aminobutyric acid (Abu) to give peptide 2. Further modifications of the Abu6 analogue (No. 2) at position one by substituting cyclohexylacetic acid (Caa), cyclohexylpropionic acid (Cpa), 1‐adamantaneacetic acid (Aaa), phenylacetic acid (Phaa), tert.‐butylacetic acid (t‐Baa), isovaleric acid (Iva), propionic acid (Pa), l‐penicillamine (P), tert.‐butoxycarbonyl (Boc) or omitting any substituent at this position, and/or in combination with Arg‐NH29, Ala‐NH2, 9d‐Arg8‐Arg‐NH29, and desGly9 modifications yielded the remaining 14 peptides. All 16 peptides were examined for agonistic and antagonistic potencies in AVP V2 and V1 assays in rats. Apart from the Cpa1 analogue and the analogue lacking any substituent in the 1‐position, all exhibit substantial V2 and V1 antagonism. A number are as potent as (A) as V2 antagonists. With an anti‐V2 pA2= 8.11 ± 0.07, Aaa‐d‐Tyr(Et)‐Phe‐Val‐Asn‐Abu‐Pro‐Arg‐Arg‐NH2 (No. 6) is as potent as any cyclic AVP V2 antagonist reported to date. The Pa1 analogue of No. 6 exhibits promising anti‐V2/anti‐V1 selectivity. These findings prove conclusively that a ring structure is not a requirement for recognition of or for binding to AVP V2 or V1 receptors. This discovery thus offers a promising new approach to the design of peptide and non‐peptide antagonists of AVP and perhaps also to other cyclic peptides such as somatostatin, atrial‐natriuretic factor, insulin, and the recently discovered endothelin. Some of these linear antagonists may be of value as pharmacological tools and as therapeutic agents.
The vasopressin precursor in the Brattleboro (di/di) rat
Authors: BIRKETT SONIA D. , PICKERING BRIAN T.
Published: August 2010

The vasopressin precursor in the rat hypothalamus has been studied, using trypsin to release desglycinamide vasopressin and coupling it to glycinamide (T&G treatment). The resulting amidated nonapeptide was detected and measured with a radioimmunoassay for vasopressin. The „vasopressin” produced in this way had the full immunoreactivity of the authentic peptide but eluted from an hplc column 1 min earlier and appeared to have a larger molecular weight. It was found that T&G treatment generated vasopressin immunoreactivity in extracts of the supraoptic nucleus (SON) of the Brattleboro rat in just the same way as it did in normal animals. Furthermore, this procedure produced vasopressin immunoreactivity in those hplc fractions from Brattleboro SON extracts that corresponded with the elution time of vasopressin precursor. Similar amounts of „vasopressin” could be generated from Brattleboro and normal SONs. These results support the suggestion that the Brattleboro SON synthesises an aberrant vasopressin precursor which is not processed by the cell.
Isolation and primary structures of elephant adrenocorticotropin and β‐lipotropin
Authors: LI CHOH HAO , OOSTHUIZEN M. M. J. , CHUNG DAVID
Published: August 2010

Adrenocorticotropin and β‐lipotropin have been isolated and purified from elephant pituitary glands. The primary structures of these two hormones were determined by amino acid and sequence analyses of enzymatically cleaved peptides from the hormones. Peptide purification involved the use of gel filtration, reverse phase high performance liquid chromatography, and paper electrophoresis.
Synthesis and biological evaluation of human preproenkephalin (100‐111) and its analogs*
Authors: IZDEBSKI JAN , BONDARUK JOLANTA , GUMUŁKA S. WITOLD , KRZAŚCIK PAWEŁ
Published: August 2010

The dodecapeptide sequence, Tyr‐Gly‐Gly‐Phe‐Met‐Lys‐Arg‐Tyr‐Gly‐Gly‐Phe‐Met (BI), which is totally conserved in the primary structures of human, bovine, rat, and toad preproenkephalins, has been synthesized by the solid‐phase method. Coupling reactions were achieved by using symmetrical anhydrides oftert.‐butyloxycarbonylamino acids preformed withN‐tert.‐butyl,N′‐methylcarbodiimide. 6‐Arg and 7‐Lys analogs have also been obtained. The peptides show opiate activity in both GPI and MVD assay, and possess antinociceptive properties as estimated by the hot‐plate test in mice when applied intracisternally.
Opioid peptides Synthesis and binding properties of dermorphin related heptapeptides
Authors: SALVADORI SEVERO , MARASTONI MAURO , BALBONI GIANFRANCO , BOREA PIERANDREA , TOMATIS ROBERTO
Published: August 2010

C‐Terminal amino acid residues of dermorphin (H‐Tyr‐D‐Ala‐Phe‐Gly‐Tyr‐Pro‐Ser‐NH2) were replaced by Nα‐methyl‐ or D‐amino acids in order to examine the effect on opioid activity. In binding studies based on displacement of μ, Δ, and κ opioid receptor selective radiolabels from guinea pig brain membranes, the 13 new analogues showed, like dermorphin, a negligible affinity for the κ binding site. The introduction of Nα‐methyl‐ or D‐amino acid residues at position 5, 6, or 7 of dermorphin, when matched with C‐terminal amide function modifications, generally produced analogues with reversed μ/δ specificity.
Chiroptical properties of aminosuccinyl peptides
Authors: CAPASSO S. , MAZZARELLA L. , SICA F. , ZAGARI A.
Published: August 2010

Circular dichroism spectra of di‐, tri‐, and tetrapeptides containing an aminosuccinyl residue (Asu) have been studied in a variety of solvents covering a wide range of polarity and hydrogen bonding ability. The CD spectral features in the longer wavelength region are determined by the chiral contribution of the Asu moiety and can be used to study the conformational preferences of these compounds in solution. In Asu tripeptides the positive band near 260 nm, which appears in non proton acceptor solvents, is correlated to an intramolecularly hydrogen bonded type II′β‐bend conformation, which previous studies have shown to be the preferred conformation in these solvents. This band can be ascribed to the asymmetrical perturbation of the succinimide chromophore induced by the carbonyl group which precedes the imide ring and is fixed at a short distance from the plane of the ring by the intramolecular hydrogen bond. The presence of this band in the CD spectra of Asu tetrapeptides indicates that these compounds also assume, in non polar solvents, the same β‐bend conformation. This interpretation is confirmed by i.r. and tH‐n.m.r. spectra, which give evidence of the presence in non polar solvents of an intramolecular hydrogen bond between the carbonyl group of the first residue and the NH group of the fourth.
1H‐n.m.r. studies on cross‐relaxation phenomena in bovine mercaptalbumin (BMA) solution and partially hydrolyzed bovine plasma albumin (BPA*) gel
Authors: ERA SEIICHI , SOGAMI MASARU , KUWATA KAZUO , FUJII HIROKO , SUZUKI EIJI , MIURA KIYOSHI , KATO KAZUO , WATARI HIROSHI
Published: August 2010

Bovine plasma albumin Fr. V(BPA) contains small amounts of proteolytic enzyme which catalyzes a very limited cleavage of BPA in the F‐form near pH 3.8, resulting in the formation of partially hydrolyzed BPA(BPA*). BPA* had a tendency to form a transparent gel at pD 4.0 (pD range of the F‐form) above 7%. Highly purified proteolytic enzyme‐free bovine mercaptalbumin (BMA) was in a transparent solution at pD 4.0 even at 12.4%. after 5 days incubation at 35°. Cross‐relaxation times (TIS) between irradiated protein protons and observed protons, such as side chain and water protons, were studied on BMA solution and BPA*‐gel. TIS values of BMA solution, obtained by the saturation transfer (SATUR) and inversion recovery (INVER) methods, were a single kind of TIS for each side chain. Those of BPA*‐gel by the SATUR method indicated the presence of two kinds of TIS, that is, short and long TIS values for each side chain. However, those by the INVER method showed a single kind of TIS for each side chain, corresponding to the long TIS value by the SATUR method. The short TIS values of BPA*‐gel, observed by the SATUR method, may be due to immobile joint parts of fibrous BPA* aggregates. TIS values from protein to water protons (TIS(HDO)) in BPA*‐gel, obtained by the INVER method, were far shorter than those in BMA solution, indicating a large amount of hydration of BPA* and rapid exchange between bound and bulk water in the gel state.
Structure and conformation of linear peptides XIII. Structure of l‐phenylalanyl‐glycyl‐glycine
Authors: SUBRAMANIAN E. , SAHAYAMARY J. JAMES
Published: August 2010

The crystal structure of a tripeptide, l‐phenylalanyl‐glycyl‐glycine (C13H17,N3O4), molecular weight = 279.3, has been determined. The crystals are orthorhombic, space group P 212121, with a= 5.462(1) A, b= 15.285(5), c= 16.056(4), Z =4, and P(calc) = 1.384 g. cm‐3. The final R‐index is 0.052 for 866 reflections with θ/λ≤ 0.55 A‐1 and 1 > σ. The molecule exists as a zwitterion, with the N‐terminus protonated and the C‐terminus in an ionized form. Both the peptide units are in the trans configuration and planar, though one of them shows significant deviations from planarity (|Δ| = 5.1°). The peptide backbone is folded, with the torsion angles of ψ1= 116.2(5)°, ψ31= 178.8(4), φ2=−89.7(5), ψ2=−28.9(6), ω2=−174.9(4), φ3= 134.9(5), ψ31= 7.8(6), ψ32=−172.6(4). The terminal glycine adopts a “d‐residue” conformation. For the sidechain of phenylalanine, χ1= 175.5(4), χ2= ‐ 127.0(6).
Analogs of oxytocin containing a pseudopeptide Leu‐Gly bond of cis and trans configuration*
Authors: LEBL MICHAL , SLANINOVÁ JIŘINA , JOHNSON RODNEY L.
Published: August 2010

Analogs of deamino‐oxytocin wherein the Leu‐Gly peptide bond has been replaced by a tetrazole moiety or by a double bond of trans configuration were synthesized and their biological activities evaluated. Trans double bond was found to be the most appropriate substitution for the amide bond (uterotonic activity 24% of the deamino‐oxytocin). In the case of all three analogs low but prolonged galactogogic activity was found and the ratio of uterotonic in vitro and in vivo activity was surprisingly high (ranging from 4.5 to 20).
Primary structure of fox pituitary growth hormone
Authors: LI CHOH HAO , IZDEBSKI JAN , CHUNG DAVID
Published: August 2010

Tryptic digests of fox growth hormone (fGH) were separated by reverse phase high performance liquid chromatography (HPLC) and by paper electrophoresis. From the amino acid composition of these tryptic peptides and from their alignment with the expected tryptic peptides from bovine growth hormone (bGH), the primary structure of fGH is proposed. There are only 17 amino acid residues which are different in these two growth hormone molecules.
Primary structure of elephant growth hormone†
Authors: HULMES JEFFREY D. , MIEDEL MAY C. , LI CHOH HAO , PAN YU‐CHING E.
Published: August 2010

The primary structure of elephant growth hormone was determined. The growth hormone was cleaved by proteolytic enzymes and cyanogen bromide. The resulting peptide fragments were separated by HPLC and then subjected to amino acid and sequence analyses. Elephant growth hormone consists of 190 amino acids with four cysteine residues. Sequence comparison with other mammalian growth hormones revealed that elephant growth hormone is highly homologous with that of pig and, to a much lesser extent, with that of human growth hormone.
Control of racemization in peptide chain elongation with an unprotected amino acid
Authors: CONRADI R.A. , BURTON P.S.
Published: August 2010

The racemization of the penultimate residue of the tripeptide prepared from Boc‐d‐Phe‐d‐Phe and free glycine in an aqueous mixed solvent system was examined. An HPLC method was developed to quantitate the amount of product with inverted stereochemistry, starting material, and other biproducts of the reaction. Depending on coupling conditions, the amount of inversion varied from less than 0.5 to nearly 25%. Using near optimal conditions (20% aqueous dioxane, 0.05 m reactants, 5°) two peptides were successfully synthesized in good yield with an acceptable extent of racemization. After recrystallization these peptides contained 0.1‐0.2% diastereomer and were recovered in 70‐74% yield. Such a prodedure could be useful for the incorporation of radiolabeled amino acids at the carboxyterminus of a peptide where minimal handling of radiolabeled intermediates is desirable.
Isolation, structure determination and synthesis of a novel tryptophan‐containing heptapeptide (basic tryptophyllin) from the skin of Phyllomedusa rohdei
Authors: MONTECUCCHI PIER CARLO , VINCENTI MARCO , LAZZARINI ANNA MARIA , RUSCONI LUISA , ERSPAMER VITTORIO
Published: August 2010

A novel tryptophyllin has been isolated from the methanol extracts of the skin of the South American frog Phyllomedusa rohdei. Its primary structure, as determined by chemical/enzymatic methods and by FAB mass spectrometry, is the following: Lys‐Pro‐Hyp‐Ser‐Trp‐Ile‐Pro‐NH2. This basic tryptophyllin has been synthesized in solid phase, in order to allow its complete pharmacological characterization.
Synthesis and biological activities of oxytocin and lysine vasopressin analogs containing glutamic acid γ‐hydrazide in position 4
Authors: GAZIS DIANA , GLASS JOHN , SCHWARTZ I. L. , STAVROPOULOS G. , THEODOROPOULOS D.
Published: August 2010

Solution methods, using N‐hydroxysuccinimide esters, were used to synthesize [Glu(NHNH2)4] oxytocin and [Glu(NHNH2)4, Lys8] vasopressin. In these analogs of neurohypophyseal hormones, the side‐chain carboxamide function of a glutamine residue is formally replaced by a hydrazide group at position 4. The hormone analogs were assayed for uterototonic activity, milk ejection activity, antidiuretic activity, and rat pressor activity. The specific biological activities of the oxytocin and vasopressin analogs were decreased compared to the respective parent hormones in all assay systems.
T.l.c. enantiomeric separation of amino acids
Authors: MARTENS J. , BHUSHAN. R.
Published: August 2010

Resolution of enantiomers is very important particularly in the fields of asymmetric synthesis, mechanistic studies, geochronology, studies of structure‐function relationship of proteins, pharmacology, and medicine. Various chromatographic methods have replaced the classical fractional crystallization, seeding and enzymatic procedures. Of these, t.l.c. provides a direct, simple, and inexpensive method for resolution of enantiomers of amino acids and their derivatives. Ligand exchange, ion exchange, and molecular inclusion complexation have been the basis of t.l.c. resolution of enantiomers of amino acids and their derivatives. The innovation of new plate types, and methods of development and detection have renewed interest in the direct resolution of enantiomers of amino acids, their derivatives and a variety of other compounds by t.l.c. The present report provides an overview of some of the more recent approaches to the direct t.l.c. resolution of amino acids and their derivatives together with special advantages and scope of t.l.c.
Conformational energy analysis of the pentapeptide Ac‐Arg‐Asn‐Cys‐Tyr‐Asn‐NMA from α1‐purothionin
Authors: FELLER DAVID C. , ZIMMERMAN S. SCOTT , VERNON LEO P.
Published: August 2010

Conformational energy analyses were carried out on the pentapeptide RNCYN (Ac‐Arg‐Asn‐Cys‐Tyr‐Asn‐NMA) and on related peptides. RNCYN is a highly conserved amino acid sequence in thionins and viscotoxins. The conformation of the pentapeptide was calculated to be an amphipathic α‐helix, with the tyrosine and cysteine on the nonpolar side of the helix and the arginine and both asparagines on the polar side. Our results are inconsistent with the conformation determined using the Chou‐Fasman prediction method, but are consistent with the conformation determined experimentally (using n.m.r.) for this pentapeptide sequence in α1‐purothionin.
Cyclic hexapeptides bearing carboxyl groups
Authors: OZEKI EIICHI , MIYAZU TAKAKO , KIMURA SHUNSAKU , IMANISHI YUKIO
Published: August 2010

Three cyclic hexapeptides bearing carboxyl groups, cyclo(l‐Asp‐l‐Phe‐l‐Pro)2 cyclo(l‐Aad‐l‐Phe‐l‐Pro)2 (Aad represents α‐amino adipic acid residue), and cyclo(d‐Asp‐d‐Phe‐l‐Pro)2 were synthesized and investigated on conformation, complexation with metal ions, and interaction with lipid membrane. These cyclic hexapeptides were found to take several different conformations, though their reference compounds, cyclo(l‐Leu‐l‐Phe‐l‐Pro)2 and cyclo[d‐ Asp(OMe)‐d‐Phe‐l‐Pro]2 took a single C2 symmetric conformation. Cyclo(d‐Asp‐d‐Phe‐l‐Pro)2 formed complexes with Ba2+ and Ca2+, whereas cyclo(l‐Asp‐l‐Phe‐l‐Pro)2 and cyclo(l‐Aad‐l‐Phe‐l‐Pro)2 did not. The latter two take amphiphilic structures and were distributed to lipid membrane more easily than cyclo(d‐Asp‐l‐Phe‐l‐Pro)2. Cyclo(d‐Asp‐l‐Phe‐l‐Pro)2 binds Ca2+ on the lipid membrane.
Use of the Npys thiol protection in solid phase peptide synthesis Application to direct peptide‐protein conjugation through cysteine residues
Authors: ALBERICIO FERNANDO , ANDREU DAVID , GIRALT ERNEST , NAVALPOTRO CARLES , PEDROSO ENRIQUE , PONSATI BERTA , RUE‐GAYO MARIANO
Published: August 2010

The protection of the thiol function of cysteine with the 3‐nitro‐2‐pyridylsulfenyl (Npys) group has been successfully applied in the solid phase synthesis of nine peptides. A reexamination of the chemical stability of the protecting group has shown that, while Npys is essentially suitable for standard Boc/benzyl synthesis conditions, it is inadequate for the Fmoc strategy. Its proven stability to “high” HF acidolysis can not be extended to “low‐high”conditions without significant thiol deprotection. On the other hand, the Npys group is quite compatible with standard photolytical cleavage conditions. The stability of Npys to HF and its thiol‐activating character allow its application in peptide‐carrier protein conjugation reactions by specific coupling through cysteine residues in the peptide.
17O, 14N and 15N n.m.r. studies of the CO2+ complexes of cyclo(Pro17O‐Gly15N) and cyclo(Gly17O‐Pro) in aqueous solution
Authors: TRITT‐GOC JADWIGA , GOC ROMAN , PONNUSAMY ETTIGOUNDER , FIAT DANIEL
Published: August 2010

The complexation of cyclo(Pro17O‐Gly15N) and cyclo(Gly17O‐Pro) with CO2+ ions has been studied by 17O, 14N and 15N n.m.r. spectroscopy in aqueous solution. 17O, 14 N and 15N transverse relaxation times and chemical shifts were measured as a function of temperature. The 17O n.m.r. studies unequivocally demonstrate that the cobaltous ion binds to the peptide oxygen of both compounds. The hyperfine coupling constant and the peptide residence times were found to be A =–0.165 MHz and – 0.145 MHz, μ= 16, and 92μsec for cyclo(Pro17O‐Gly15N) and cyclo(Gly17O‐Pro), respectively. The 14N and 15N studies of labeled cyclo(Pro17O‐Gly15N) do not indicate binding at either the Gly15N or the Pro14N site.
Thio‐α‐amino acids (S‐acids) as a carboxyl component in peptide synthesis catalysed by papain
Authors: MITIN YU.V. , ZAPEVALOVA N.P.
Published: August 2010

Peptide synthesis catalysed by papain was studied using thio‐α‐amino acids (S‐acids) as a carboxyl component. It was found, for example, that with Z‐AlaSH (pK 2.70) the maximal yield of the peptide Z‐AlaValNH2 was obtained at pH 8–8.5. A two‐fold excess of Z‐AlaSH furnished peptides with yields close to 100%. Thio‐amino acids with bulky side groups, for example, Z‐IleSH, Z‐Asp(OBut)SH, gave peptides with a low yield. Papain interacts with Z‐AlaSH better than do bromelain or ficin.
Synthesis and conformational studies of peptides encompassing the carboxy‐terminal helix of thermolysin
Authors: VITA CLAUDIO , DALZOPPO DANIELE , DE FILIPPIS VINCENZO , LONGHI RENATO , MANERA ERNESTO , PUCCI PIERO , FONTANA ANGELO
Published: August 2010

The 21‐residue fragment Tyr‐Gly‐Ser‐Thr‐Ser‐Gln‐Glu‐Val‐Ala‐Ser‐Val‐Lys‐Gln‐Ala‐Phe‐Asp‐Ala‐Val‐Gly‐Val‐Lys, corresponding to sequence 296–316 of thermolysin and thus encompassing the COOH‐termi‐nal helical segment 301–312 of the native protein, was synthesized by solid‐phase methods and purified to homogeneity by reverse‐phase high performance liquid chromatography. The peptide 296–316 was then cleaved with trypsin at Lys307 and Staphylococcus aureus V8 protease at Glu302, producing the additional fragments 296–307, 308–316, 296–302, and 303–316. All these peptides, when dissolved in aqueous solution at neutral pH, are essentially structureless, as determined by circular dichroism (CD) measurements in the far‐ultraviolet region. On the other hand, fragment 296–316, as well as some of its proteolytic fragments, acquires significant helical conformation when dissolved in aqueous trifluoroethanol or ethanol. In general, the peptides mostly encompassing the helical segment 301–312 in the native thermolysin show helical conformation in aqueous alcohol. In particular, quantitative analysis of CD data indicated that fragment 296–316 attains in 90% aqueous trifluoroethanol the same percentage (∼58%) of helical secondary structure of the corresponding chain segment in native thermolysin. These results indicate that peptide 296–316 and its subfragments are unable to fold into a stable native‐like structure in aqueous solution, in agreement with predicted location and stabilities of isolated subdomains of the COOH‐terminal domain of thermolysin based on buried surface area calculations of the molecule
Monobiotinylated relaxins
Authors: BÜLLESBACH ERIKA E. , SCHWABE CHRISTIAN
Published: August 2010

Biotinylated porcine relaxins were synthesized and purified to homogeneity. Native porcine relaxin was reacted with biotinyl‐E‐aminohexanoic acid‐N‐hydroxysuccinimide ester and the resulting mixture was separated by either ion exchange chromatography on CM‐cellulose at pH 5.5 or reversed‐phase high performance liquid chromatography. All four possible monosubstituted relaxin derivatives, with substitutions in NαA1, NεA7, NεA16, and NεB8, were obtained. All derivatives were fully biologically active and comparative circular dichroism spectroscopy showed no significant differences in their secondary structure.
Competition between tuftsin and HBV S‐protein sequences
Authors: SIEMION IGNACY Z. , SŁON JACEK , NAWROCKA ELEONORA , WIECZOREK ZBIGNIEW
Published: August 2010

The syntheses of HBV S‐protein partial sequences: Thr‐Lys‐Pro‐Thr (I), Thr‐Lys‐Pro‐Thr‐Asp (II), and Thr‐Lys‐Pro‐Thr‐Asp‐Gly (III) and also of pentapeptide Thr‐Lys‐Pro‐Gly‐Arg (IV), are described. For the peptides II and III inhibitory activity against tuftsin was found. Peptide IV (an analogue of tuftsin‐inhibitor Thr‐Lys‐Pro‐Pro‐Arg) demonstrated a tuftsin‐like activity in the phagocytosis experiments.
Application of acetamidomethyl and 9‐fluorenylmethyl groups for efficient side protection of penicillamine in solid‐phase peptide synthesis
Authors: GARCÍA‐ECHEVERRÍA CARLOS , MOLINS M. ANTONIA , ALBERICIO FERNANDO , PONS MIQUEL , GIRALT ERNEST
Published: August 2010

Synthesis of S‐acetamidomethyl and S‐fluorenylmethyl derivatives of penicillamine is described. Both groups are completely stable to all the usual reagents in solid‐phase peptide synthesis, including the HF cleavage step, and show an excellent degree of orthogonality to each other. Treatment of the protected peptides Ac‐L‐Pen(X)‐L‐Pro‐D‐Val‐L‐Cys(X)‐NH2 with thallium (III) trifluoroacetate or iodine for X = Acm or piperidine/DMF (1:1) for X = Fm induced with good yield the formation of the intramolecular disulfide bridge. This cyclic peptide appears to assume a type II β‐turn conformation in d6‐DMSO as evidenced by 1H‐NMR spectra.
Preparation and opioid activities of N‐methylated analogs of [D‐Ala2, Leu5]enkephalin
Authors: KAWAI MASAO , FUKUTA NORIHITO , ITO NAOKI , KAGAI TAKATOYO , BUTSUGAN YASUO , MARUYAMA MUTSUMI , KUDO YOSHIHISA
Published: August 2010

Analogs of opioid pentapeptide [D‐Ala2, Leu5]enkephalin were prepared using two kinds of N‐methylation reactions, namely quaternization and amide‐methylation. Quaternization reaction with CH3I‐KHCO3 in methanol was applied to the deprotected N‐terminal group of the pentapeptide derivatives affording trimethylammonium group‐containing analogs. [Me3+ Tyr1,D‐Ala2, Leu5]enkephalin and its amide were found to show opioid activity on guinea pig ileium assay only slightly lower than the parent unmethylated peptides. Application of amide‐methylation reaction using CH3I‐Ag2O in DMF to the protected pentapeptide yielded a pentamethyl derivative in which all of the five N atoms were methylated. Deprotection of the derivative gave pentamethyl analogs of [D‐Ala2, Leu5]enkephalin, which showed no significant activity on the guinea pig ileum assay and opiate‐receptor binding assay.
Structure and conformation of peptides involving prolyl residue
Authors: PANNEERSELVAM K. , CHACKO K.K.
Published: August 2010

The dipeptide, L‐prolyl‐L‐leucine monohydrate (C11 H20 N2 O3· H2O, molecular weight, 246.3) crystallizes in the monoclinic space group P21/, with cell constants: a = 6.492(2)Å b = 5.417(8)Å c = 20.491(5)Å, β= 96.59(2)°, Z = 2, Do = 1.15g/cm3, and Dc = 1.142g/cm3. The structure was solved by SHELX‐86 and refined by full matrix least squares methods to a final R‐factor of 0.081 for 660 unique reflections (I > 2σ (I)) measured on an Enraf Nonius CAD‐4 diffractometer (CuKx, λ= 1.5418 4AR, T = 293 K). The peptide linkage exists in the trans conformation. The pyrrolidine ring exists in the envelope conformation. The values of the sidechain torsion angles are: ψ1= ‐59.3(13)°, ψ21= ‐63.1(16)° and ψ22= 174.8(15)° for leucine (C‐terminal). The crystal structure is stabilised by a three‐dimensional network of N—H… O, O—H… O, and C—H…O hydrogen bonds.
Interaction of gramicidin S analogs with lipid bilayer membrane
Authors: YAGI YOSHIKO , KIMURA SHUNSAKU , IMANISHI YUKIO
Published: August 2010

One of the side chains of Orn residues in gramicidin S (GS) was connected with alanine (AGS), sarcosine (SGS), or histidine (HGS) residue, aiming at developing membrane‐active artificial enzymes by virtue of the membrane‐associating property of GS. The conformation of the GS analogs was similar to that of GS. However, the affinity of GS and its analogs for dipalmitoylphosphatidylcholine (DPPC) vesicles decreased in the order of GS > SGS > HGS ≃ AGS. The addition of GS analogs at 10 μ to DPPC vesicles decreased the membrane fluidity, indicating that GS analogs did not disrupt the vesicular structure of DPPC vesicles. On the other hand, GS analogs enhanced carboxyfluorescein‐leakage from DPPC vesicles. It was therefore considered that the GS analogs induced the phase‐separation of the lipid bilayer membrane. Hydrolytic reactions of HGS in the presence of DPPC vesicles were studied using N‐methylindoxyl alkanoate as substrate. HGS reacted only with N‐methylindoxyl hexanoate below the phase‐transition temperature of the membrane. The substrate specificity of HGS was ascribed to the condensation of HGS in the neighbourhood of the substrate in the lipid bilayer membrane due to the phase‐separation below the phase‐transition temperature of the membrane.
Continuous‐flow solid‐phase synthesis of potential antigenic peptides of hepatitis B virus
Authors: RABANAL F. , HARO I. , REIG F. , GARCÍA‐ANTÓN J.M.
Published: August 2010

The synthesis of three hepatitis B surface antigens derived from S and pre‐S proteins (adw S(140–147), [Tyr148] adw S(139–148), and adw pre‐S (120–145)) has been accomplished by the continuous flow Fmoc‐polyamide solid phase method. The use of different scavengers and trimethylsilyl bromide (TMSBr) in trifluoroacetic acid as deprotecting procedures is discussed.
Conformational features responsible for binding of cyclic analogues of enkephalin to opioid receptors
Authors: NJKIFOROVICH GREGORY V. , BALODIS JURIS , SHENDEROVICH MARK D. , GOLBRAIKH ALEXANDER A.
Published: August 2010

Low‐energy peptide backbone conformers were found by means of energy calculation for several cyclic analogues of enkephalin in an attempt to assess models for receptor‐bound conformations for opioid receptors of the μ‐ and §‐types. They included [D‐Cys2, L‐Cys5]‐ and [D‐Cys2, D‐Cys5]‐enkephalinamides showing moderate preference for preceptors, the selective compounds [D‐Pen2, L‐pen5] and [D‐Pen2, D‐Pen5]‐enkephalins and Tyr‐D‐Lys‐Gly‐Phe analogue possessing very high affinity to receptors of the μ‐type. The low‐energy conformers obtained for these analogues were in good agreement with the results of calculations by other authors and with experimental evidence. All of the analogues contain a Phe residue in position 4 of the peptide chain which facilitates the eventual search for geometrical similarity between the low‐energy backbone conformers of different analogues in question.
BOP reagent for the coupling of pGlu and Boc‐His(Tos) in solid phase peptide synthesis
Authors: FOREST MYLÈNE , FOURNIER ALAIN
Published: August 2010

The model peptide TRH was successfully synthesized using benzotriazol‐l‐yl‐oxy‐tris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent). The coupling reactions were carried out in N,N‐dimethylformamide or N‐methylpyrrolidone. These solvents allowed the incorporation of the N‐terminal pyroglutamic acid residue into the peptide chain, without using the derivative bearing the N‐benzyloxycarbonyl group, which acts as a solubility promoter. A comparative racemization study showed that Boc‐His(Tos) can be coupled by means of BOP reagent with less racemization than with DCC when the amount of diisopropylethylamine (DIEA) is kept minimal (same ratio of equivalents as for Boc‐His(Tos), i.e. 3 equiv.). However, with the use of a larger amount of DIEA in the coupling mixture (9 equiv.), approximately 3% of epimer was found in the crude product. Our study showed that even under low DIEA conditions, the rate of coupling of the residues with BOP remained comparable to that observed with DCC.
Synthesis and purification of two SP (6–11) analogues with enhanced selectivity for the NK‐1 receptor
Authors: HARO I. , TORRES J.L. , VALENCIA G. , ANTON J.M. GARCIA , REIG F.
Published: August 2010

Two hexapeptide analogues of Substance P (6–11) have been synthesized. Replacement of Gly9 by proline provides a peptide with tenfold enhanced selectivity for the NK‐1 receptor. The corresponding proline‐containing glycopeptide incorporating a β‐d‐glucopyranosyl residue linked to the side‐chain of Glus was 100 times more selective than Substance P for the same receptor.
Synthetic peptide models for protein secondary structures β‐Sheet formation in acyclic cystine peptides
Authors: BALARAM HEMALATHA , UMA K. , BALARAM P.
Published: August 2010

The conformations of the symmetrical cystine peptides Boc‐Cys ‐(Val)n ‐Trp‐OMe Boc‐Cys‐(Val)n ‐Trp‐OMe (n = 1, 1; 2, 2; 3, 3) have been examined in solution, in order to evaluate the use of disulfide crosslinks in stabilizing extended β‐strand conformations in acyclic sequences. NMR studies in (CD3)2 SO provide evidence for the solvent inaccessible nature of the Val (2) NH group in peptides 1 and 2. JHNCHxH values are indicative of extended structures. Sequential interresidue nuclear Overhauser effects support the population of β‐strand structures in both peptides. The fluorescence quantum yield of tryptophan determined in methanol follows the order 2 > 1 ñ 3. Reduction of the disulfides with NaBH4 results in large enhancements of emission intensity, with the changes following the order 1 > 3 > > 2. The order of quenching is a function of the disposition of the indole and disulfide sidechains in an extended beta;‐sheet structure.
Orthogonal solid‐phase synthesis of human gastrin‐I under mild conditions*
Authors: KNEIB‐CORDONIER NANCY , ALBERICIO FERNANDO , BARANY GEORGE
Published: August 2010

An approach to the solid‐phase segment condensation synthesis of the 17‐peptide amide human gastrin‐I has been developed. Nα‐amino and side‐chain protection were provided by 9‐fluorenylmethyloxycarbonyl (Fmoc) and tert.‐butyl groups, and a series of anchors cleavable under mild conditions were used. The N‐terminal pentapeptide pGlu‐Gly‐Pro‐Trp‐Leu‐OH was prepared using a p‐alkoxybenzyl ester linkage made by a preformed handle strategy. Cleavage, in 65% yield, was with the new Reagent M: CF3 COOH—CH2 Cl2—β‐mercaptoethanol‐anisole (70:30:2:1), which was optimized to preserve the labile tryptophan residue. A new preformed handle procedure expedited solid‐phase synthesis of the protected “middle” hexapeptide, Fmoc‐(Glu(OtBu))5‐Ala‐OH, anchored as an o‐nitrobenzyl ester. Chains were not lost during this assembly, and final photolytic cleavage (350nm) in toluene—CF3 CH2 OH (4:1) occurred in 59% yield. Both protected intermediates were purified by simple gel filtration, whereupon they were shown to be pure by analytical HPLC, and gave satisfactory NMR and FABMS spectra. Last, the C‐terminal hexapeptide, Tyr(tBu)‐Gly‐Trp‐Met‐Asp(OtBu)‐Phe, was assembled on a tris(alkoxy)benzylamide “PAL” support. For the polymer‐supported segment condensation, the middle and N‐terminal pieces were added respectively in > 98% and 89% yields (judged by amino acid analysis and solid‐phase sequencing), by overnight couplings in N,N‐dimethylformamide (DMF) mediated by benzotriazolyl N‐oxytrisdimethylaminophosphonium hexafluorophosphate (BOP) in the presence of 1‐hydroxybenzotriazole (HOBt) and N‐methylmorpholine (NMM). Racemization was 4% and 11% respectively at Ala and Leu. Cleavage with Reagent M followed by reversed‐phase chromatography gave pure gastrin‐I in an overall 30% isolated yield. These results compare favorably with those from a stepwise assembly.
Cholecystokinin analogues with high affinity and selectivity for brain membrane receptors*
Authors: HRUBY VICTOR J. , FANG SUNAN , KNAPP RICHARD , KAZMIERSKI WIESLAW , LUI GEORGE K. , YAMAMURA HENRY I.
Published: August 2010

A series of CCK analogues in which positions 28 and 31 have been replaced by N‐methylnorleucine residues have been synthesized. It has been found that most of these N‐methylnorleucine containing analogues of CCK are highly potent and some are extraordinarily selective for the central vs. peripheral receptor in two animal models (guinea pig and rat). [N‐MeNle28.31] CCK26–333 nonsulfated exhibited both high potency (IC50= 0.13 nM) and selectivity for central vs. peripheral receptors. The pancrease to brain cortex binding affinity ratio for this analogue IS 5100 in the rat model. NMR studies reveal that there is cis/trans isomerism about the N‐methylnorleucine residue that may be related to high selectivity.
Properties of a cleaved two‐chain form of recombinant human growth hormone
Authors: CANOVA‐DAVIS ELEANOR , BALDONADO IDA P. , MOORE JEROME A. , RUDMAN CHRISTOPHER G. , BENNETT WILLIAM F. , HANCOCK WILLIAM S.
Published: August 2010

Escherichia coli cells transformed with plasmids engineered for the expression of recombinant human growth hormone as a secreted product also produced a proteolytically cleaved form of rhGH. This variant is isolated at a high resolution anion exchange chromatography stage during the manufacturing process. The higher isoelectric point of this form is demonstrated by isoelectric focusing and chromatofocusing and the two‐chain nature by tryptic mapping, N‐ and C‐terminal sequence analyses, and sodium dodecyl sulfate polyacrylamide gel electrophoresis. These data indicate that the single site of cleavage is between Thr‐142 and Tyr‐143, in contrast to the two‐chain variant isolated from human pituitary glands, which has a clip after residue Phe‐139. The recombinant two‐chain form was further characterized by reversed‐phase high performance liquid chromatography at both acidic and basic pHs. The assay utilizing bicarbonate‐containing mobile phases was determined to be the most efficient and sensitive method. The bioactivity of this two‐chain form was measured by the in vivo rat weight gain assay and by the in vitro Nb2 cell bioassay. Its immunological similarity to intact one‐chain rhGH was demonstrated with an enzyme‐linked immunosorbent assay.
Morphiceptin analogs containing 2‐aminocyclopentane carboxylic acid as a peptidomimetic for proline
Authors: MIERKE DALE F. , NÖßNER GERHARD , SCHILLER PETER W. , GOODMAN MURRAY
Published: August 2010

As part of a program to study the structure‐activity relationship of peptide opioids we report the synthesis, conformational characterization and biological activity of four analogs related to morphiceptin in which the proline at position two has been substituted with 2‐aminocyclopentane carboxylic acid (βAc5c). The βAc5c residue is a beta amino acid with two chiral centers resulting in four possible configurations; two configurationalcis(R,S and S,R) and two configurationaltrans(R,R and S,S) forms. Utilizing high resolution n.m.r. at 500 MHz and computer simulations with NOE restraints the chirality of the βAc5c residues are assigned. The analog containing the R,S‐βAc5c is active at both the μ and δ‐opioid receptors, with a slight preference for the μ‐receptor. The (S,R), (S,S), and (R,R) analogs show minimal activity at the μ‐receptor and are inactive at the δ‐receptor. A comparison of the findings from the conformational analysis and biological assays lends insight into the structure‐activity relationship of this important peptide opiate.
Synthesis of β and γ‐fluorenylmethyl esters of respectively Nα‐Boc‐L‐aspartic acid and Nα‐Boc‐L‐glutamic acid
Authors: AL‐OBEIDI FAHAD , SANDERSON DOUGLAS G. , HRUBY VICTOR J.
Published: August 2010

The orthogonal synthesis of Nx‐Boc‐L‐aspartic acid‐γ‐fluorenylmethyl ester and Nα‐Boc‐L‐glutamic acid‐δ‐fluorenylmethyl ester is reported. This is a four‐step synthesis that relies on the selective esterification of the side‐chain carboxyl groups on Nx‐CBZ‐l‐aspartic acid and Nα‐CBZ‐l‐glutamic acid. Such selectivity is accomplished by initially protecting the a‐carboxyl group through the formation of the corresponding 5‐oxo‐4‐oxazolidinone ring. Following side‐chain esterification, the α‐carboxyl and α‐amino groups are deprotected with acidolysis. Finally, the α‐amino group is reprotected with the t‐butyl‐oxycarbonyl (Boc) group. Thus aspartic acid and glutamic acid have their side‐chain carboxyl groups protected with the base‐labile fluorenylmethyl ester (OFm) and their α‐amino groups protected with the acid‐labile Boc group. These residues, when used in conjunction with Nx‐Boc‐Nε‐Fmoc‐l‐lysine, are important in the formation of side‐chain to side‐chain cyclizations, via an amide bridge, during solid‐phase peptide synthesis.
An improved solid‐phase synthesis of a difficult‐sequence peptide using hexafluoro‐2‐propanol
Authors: MILTON SASKIA C.F. , MILTON R.C. DE L.
Published: August 2010

The polar solvent 1,1,1,3,3,3‐hexafluoro‐2‐propanol was used, diluted with dichloromethane, to improve the extent and time of aminoacylation and acetylation in the solid‐phase synthesis of a difficult‐sequence peptide (the d‐Ala17 analog of the human gonadotropin‐releasing hormone precursor peptide fragment 14‐36) which characteristically exhibits chronic repetitive incomplete peptide bond formation.
Acid‐catalyzed hydrolysis of peptide‐amides in the solid state
Authors: TEN KORTENAAR PAUL B.W. , HENDRIX BERT M.M. , VAN NISPEN JAN W.
Published: August 2010

The hydrolysis of peptide‐amides in the solid state at 4° due to the presence of residual strong acid was investigated. It was found that even small molar excesses of these acids cause substantial deamidation in one day. The degree of amide hydrolysis depends not only upon the pKa and the volatility of the acid, but also upon the accessibility of the amide function; peptides with bulky C‐terminal residues are more stable than the less‐hindered ones.
Predicting isomorphic residue replacements for protein design
Authors: TÜDÖS E. , CSERZÖ M. , SIMON I.
Published: August 2010

The replaceability of amino acids as reflected in their neighbourhood selectivity is analyzed in this paper. Neighbourhood selectivity was found to be more characteristic of the individual amino acids than the other commonly used parameters. The residue replacement rank obtained was compared with other proposed ranks and was tested on naturally accepted point mutations in homologous proteins.
Synthesis and in vitro and in vivo activity of analogs of growth hormone‐releasing hormone (GH‐RH) with C‐terminal agmatine
Authors: ZARANDI MARTA , CSERNUS VALER , BOKSER LAZARO , BAJUSZ SANDOR , GROOT KATE , SCHALLY ANDREW V.
Published: August 2010

In the search for more active analogs of human growth hormone‐releasing hormone (GH‐RH), 37 new compounds were synthesized by solid phase methodology, purified, and tested biologically. Most of the analogs contained a sequence of 27 amino acids and N‐terminal desaminotyrosine (Dat) and C‐terminal agmatine (Agm), which are not amino acids. In addition to Dat in position 1 and Agm in position 29, the majority of the analogs had Ala15 and Nle27 substitutions and one or more additional L‐ or D‐amino acid modifications. [Dat1, Ala15, Nle27]GH‐RH(1‐28)Agm (MZ‐2‐51) was the most active analog. Its in vitro GH‐releasing potency was 10.5 times higher than that of GH‐RH(1‐29)NH2 and in the i.v. in vivo assay, MZ‐2‐51 was 4‐5 times more active than the standard. After s.c. administration to rats, MZ‐2‐51 showed an activity 34 times higher at 15min and 179 times greater at 30min than GH‐RH(1‐29)NH2 and also displayed a prolonged activity. D‐Tyr10, D‐Lys12, and D‐Lys12 homologs of MZ‐2‐51 also showed enhanced activities. Thus, [Dat1, D‐Tyr10, Ala15, Nle27]GH‐RH(1‐28)Agm (MZ‐2‐159), [Dat1, D‐Lys12, Ala15, Nle27]GH‐RH(1‐28)AGM (MZ‐2‐57), and [Dat1, Ala15, D‐Lys21, Nle27]GH‐RH(1‐28)Agm (MZ‐2‐75) were 4‐6 times more active in vitro than GH‐RH(1‐29)NH2. In vivo, after i.v. administration, analog MZ‐2‐75 was equipotent and analogs MZ‐2‐159 and MZ‐2‐57 about twice as potent as the standard. After S.C. administration, the potencies of MZ‐2‐57 and MZ‐2‐75 were 10‐14 times higher than the standard at 15 min and 45‐89 times greater when determined at 30 min. Most of the analogs containing two or more D‐amino acid substitutions were less active than GH‐RH(1‐29)NH2 or inactive. Our studies indicate that very potent GH‐RH analogs can result from the combination of agmatine in position 29 with other substitutions.
Synthetic peptides including acidic clusters as substrates of yeast casein kinase‐2
Authors: MARIN ORIANO , CALDERAN ANDREA , RUZZA PAOLO , BORIN GIANFRANCO , MEGGIO FLAVIO , GRANKOWSKI NIKODEM , MARCHIORI FERNANDO
Published: August 2010

The synthesis is reported of a series of glutamyl peptide analogs of the model substrate H‐Ser‐Glu‐Glu‐Glu‐Glu‐Glu‐OH of casein kinase‐2 (CK‐2). A convenient HPLC method for the separation of slightly different acidic peptides is also reported. The site specificity of yeast casein kinase‐2 (Y‐CK2) is examined with the aid of synthesized peptide substrates.
A side reaction in solid phase synthesis Insertion of glycine residues into peptide chains via Nim→ Nα transfer
Authors: KUSUNOKI MARIKO , NAKAGAWA SHIZUE , SEO KAEKO , HAMANA TAKUMI , FUKUDA TSUNEHIKO
Published: August 2010

In solid‐phase peptide synthesis using Nα‐Boc‐Nim‐tosyl‐histidine (Boc‐His(Tos)), byproducts having extra Gly residues in the peptide chain were observed at a high rate. When a Boc‐amino acid such as Asn was incorporated after assembly of Boc‐His(Tos), the Nim‐tosyl group was partially or fully cleaved by an activating agent, 1‐hydroxybenzotriazole. In the successive coupling reactions, Boc‐Gly was incorporated into the free Nim ring as well as the α‐amino function, and the Nim‐Gly was then transferred to the α‐amino group of Gly of the peptide chain after removal of these Boc groups to give extra Gly residues at the position of Gly. This was observed in only the coupling reaction with Boc‐Gly and could be circumvented using a more stable Nim protecting group for His, such as a dinitrophenyl group.
Quantitative structure‐activity relationships for sea anemone polypeptide toxins
Authors: HELLBERG SVEN , KEM WILLIAM R.
Published: August 2010

Sea anemone polypeptides vary considerably in their affinities for sodium channels occurring in different excitable cells. The amino acid sequence variation in a set of six sea anemone type I polypeptide toxins (46–49 residues long), was parameterized using descriptor scales z1, z2, and z3, derived from a large number of amino acid physicochemical properties. The pharmacological properties of the toxins were represented by the results from four bioassays on crab, mouse, and rat brain and from rat heart. By means of the descriptor scales and the multivariate data analytical method PLS (partial least squares projections to latent structures), it was possible to develop quantitative structure‐activity relationships (QSAR). Using the QSARs derived from the set of six polypeptide toxins the pharmacological properties of two homologous sea anemone polypeptide toxins were predicted. Thus it is shown that QSARs may be formulated for relatively long bioactive polypeptides. The QSARs indicate that 11 different amino acid positions may be of importance, but that positions no. 5, 21, 28, 34, 37, and 40 were of main importance in modeling the relative toxicities of the six polypeptides.
High‐performance liquid chromatography of 2,4‐disubstituted‐5(4H)‐oxazolones, anhydrides and other activated forms of N‐acyl‐ and N‐alkoxycarbonylamino acids
Authors: CHEN FRANCIS M.F. , BENOITON N. LEO
Published: August 2010

Normal phase high‐performance liquid chromatography has been achieved of the common activated forms of valine on a LiChrosorb‐CN or a μPorasil (underivatized silica) column using hexane containing 1.5 or 5%tert.‐butanol as solvent. Compounds examined include the 2‐alkoxy‐5(4H)‐oxazolones and symmetrical and mixed anhydrides of N‐tert.‐butoxycarbonyl‐, N‐benzyloxycarbonyl‐, and N‐9‐fluorenylmethoxycar‐bonylvaline, the chloride of the latter, a p‐nitrophenyl ester, 2‐methyl‐4‐isopropyl‐5(4H)‐oxazolone, valine‐N‐carboxyanhydride, and the N‐ and O‐ethoxycarbonyl adducts of 1‐hydroxybenzotriazole. The 5(4H)‐ox‐azolones from N‐tert.‐butoxycarbonylvaline and N‐benzyloxycarbonylglycylvaline decomposed during chromatography on the μPorasil but not the LiChrosorb‐CN column. The method allows direct monitoring of reactions involving generation or consumption of activated forms of amino acids.
Peptide amphipathy: a new strategy in design of potential insecticides
Authors: FROHLICH DONALD R. , WELLS MICHAEL A.
Published: August 2010

A 30‐residue peptide [YAA(KALA)6LAA] with an amphipathic helix repeat unit of Lys‐Ala‐Leu‐Ala (KALA) was synthesized as both the l‐ and the d‐isomer. The peptide was shown to form α‐helices and lyse lipid vesicles in a pH dependent fashion. The calculated helical amphipathic moment is + 1.19 kcal/ residue and the mean residue hydrophobicity is +0.4 kcal/residue. The formation of α‐helices as the pH is increased is similar to poly‐lysine, yielding a pK of 10.2. Though not toxic when fed to insects, KALA killed Spodoptera frugiperda cells at low doses and Manduca sexta larvae when injected.