bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformation of some oligopeptides containing Lys, Ala, and Tyr
Authors: CAMPOS J.L. , AYMAMÍ J. , PORTUGAL J. , SUBIRANA J.A. , MAYER R.
Published: August 2010

We have studied by X‐ray diffraction and infrared spectroscopy the structure of the following peptides: N‐acetyl‐Lys‐Ala‐Tyr‐Ala‐Lys‐ethylamide; N‐acetyl‐Lys‐d(Ala)‐Tyr‐Ala‐Lys‐ethylamide; N‐acetyl‐Lys‐Ala‐Lys‐Ala‐Lys‐ethylamide; N‐acetyl‐Lys‐Ala‐Lys‐ethylamide and N‐acetyl‐Tyr‐Ala‐Lys‐ethyalmide. All of them show a cross‐β structure, most likely with an antiparallel organization of the peptide chains. The d‐Ala residue present in one of the peptides apparently does not interfere with the formation of the pleated‐sheet structure. Due to the sequence of the peptides we have used, most of them are organized in double layers: one hydrophobic, containing the methyl groups of alanine, and the other one hydrophilic, containing the lysine side chains. Tyrosine is also found in the latter layer.
Synthesis of side‐chain to side‐chain cyclized peptide analogs on solid supports
Authors: SCHILLER PETER W. , NGUYEN THI M.‐D. , MILLER JACK
Published: August 2010

Cyclic peptide structures of the type ‐Lys‐R1—Rn‐Glu‐ can be synthesized on the Merrifield resin by assembling the peptide chain using Nα‐Fmoc‐amino acids and Boc and tert.‐butyl protection for the side‐chains of Lys and Glu, respectively. If residues R1 to Rn contain side‐chain functional groups, TFA‐resistant protection is required. After TFA treatment cyclization on the resin can be performed with appropriate coupling reagents. The formation of such cyclic structures may be preceded or followed by peptide chain assembly using Nα‐Boc‐amino acids and the entire peptide chain containing the cyclic portion is finally cleaved by HF treatment. Using this principle we synthesized the following opioid peptide related cyclic analogs: H‐Tyr‐d‐Lys‐Gly‐Phe‐Glu‐NH2 (I), H‐Tyr‐Lys‐Gly‐Phe‐Glu‐NH2 (II), H‐Tyr‐d‐Lys‐Phe‐Glu‐NH2 (III), H‐Tyr‐d‐Glu‐Gly‐Phe‐Lys‐NH2 (IV), H‐Tyr‐d‐Glu‐Phe‐Lys‐NH2 (V), H‐Tyr‐d‐Orn‐Gly‐Glu‐NH2 (VI) and H‐Tyr‐d‐Ala‐Lys‐Phe‐Glu‐NH2 (VII). Cyclic monomers were obtained in all cases, as demonstrated by mass spectrometry. Analysis of side‐products revealed a slow‐down of the HF deprotection of O‐benzylated tyrosine as a consequence of hydrophobic interactions as well as the formation of a side‐chain‐linked antiparallel cyclic dimer in the case of compound VI. In conclusion, the described method permits the convenient preparation of peptide analogs cyclized via amide bond formation between side‐chain amino and carboxyl groups in reasonable yield.
Peptide synthesis on the new polyoxyethylene‐polystyrene graft copolymer, synthesis of insulin B 21–30
Authors: BAYER ERNST , DENGLER MICHAEL , HEMMASI BAHRAM
Published: August 2010

An insoluble graft copolymer composed of the covalently bound polyoxyethylene to cross‐linked polystyrene‐divinylbenzene was employed as the solid support for peptide synthesis. The physical properties of this new polymeric support were similar to those of the cross‐linked polystyrene. Thus, identical manipulations such as shaking and filtration could be performed on this resin. The graft copolymer was used for the synthesis of the C‐terminal decapeptide of bovine insulin B‐chain in the usual solid‐phase manner. The protected peptide was cleaved from the polymeric support by photolysis and was purified by chromatography on silica gel and Sephadex LH‐20. Samples of the decapeptide were treated with liquid HF and the unprotected peptide was purified by ion‐exchange chromatography. The free peptide was shown to be homogeneous by HPLC, electrophoresis and t.l.c. The identity of this peptide was also confirmed by FAB‐MS and amino acid analysis. The synthesized peptides were shown to be free of racemization. The free peptide possesses a disordered conformation as revealed by the CD measurement.
Synthesis, purification and characterization of thymosin α11, a new thymic peptide
Authors: HEIMER E.P. , AHMAD M. , LAMBROS T.J. , FELIX A.M.
Published: August 2010

A synthesis of thymosin α11, a new 35 amino acid thymic peptide structurally related to thymosin α1 (J. Caldarella, G.J. Goodall, A.M. Felix, E.P. Heimer, S.B. Salvin & B.L. Horecker (1983) Proc. Natl. Acad. Sci US 80, 7424–7427), is reported. The synthesis was accomplished by the solid phase method employing the 4‐(aminoacyloxymethyl) phenylacetamidomethyl(Pam)‐copoly(styrene‐1% divinylbenzene) resin. The synthetic material was purified by preparative high pressure liquid chromatography and was found to be equivalent to the natural compound in its chemical properties.
Synthesis of partial sequences of ribosomal proteins and their derivatization with acryloyl residues
Authors: ECKSTEIN HEINER , HU ZHENG , SCHOTT HERBERT , BAYER ERNST
Published: August 2010

Peptide sequences B‐X‐B (B = Arg and/or Lys; X = Glu or Asp) are of considerable interest because of their possible interactions with ribosomal RNA. The syntheses of various protected peptides with the sequence Ala‐B‐X‐B‐Ala (X = Glu or Ala) and [Arg]n‐Pro (n = 1–3) are described. They are carried out in solution according to the conventional peptide synthesis method. The carbobenzoxy group is used for Nα‐protection and the methyl group for the protection of the terminal carboxyl group. The side chains of Lys and Glu are respectively blocked with the tert.‐butyloxycarbonyl and the tertiary butyl group and the guanidinic function of arginine with the NO2‐group. The intermediate peptides are purified either by extraction or by size exclusion chromatography. A specially adapted strategy of peptide synthesis allows removal of the amino terminal Cbo‐group at the end of the synthesis and introduction of an acryloyl group. By radical copolymerization with cross‐linking agents these acryloyl derivatives can be transferred into insoluble peptide gels suitable for affinity chromatography and for investigating peptide‐oligonucleotide interactions. The isolation of the unprotected peptides Arg‐Arg‐Arg‐Pro, Ala‐Arg‐Glu‐Arg‐Ala, Ala‐Arg‐Glu‐Lys‐Ala, Ala‐Arg‐Ala‐Lys‐Ala, Ala‐Lys‐Glu‐Lys‐Ala and their characterization using amino acid analysis, electrophoresis, and FAB‐mass spectrometry is also reported.
Solution conformations of valinomycin‐divalent cation complexes
Authors: SANKARAM M.B. , EASWARAN K.R.K.
Published: August 2010

The solution conformations of complexes of valinomycin with magnesium and strontium were investigated by circular dichroism, nuclear magnetic resonance and infrared techniques. The results were compared with our earlier results on lithium, calcium, manganese and barium complexes. All these cations, except lithium, form 2:1 ion sandwich and 1:1 carrier‐cation complexes with valinomycin. The 1:1 complex has a conformation different from that of the valinomycin‐potassium complex. Lithium forms only the 1:1 complex. Strontium and barium form a large number of 1:2 complexes with open conformations rapidly interconverting in solution in addition to the above 2:1 and 1:1 complexes. These observations are rationalized taking into account the ionic radii and coordination numbers of the cations and the conformational restraints of valinomycin molecules. It is suggested that cations with co‐ordination numbers of about six (magnesium and calcium) form the 2:1 and 1:1 complexes whereas those with higher co‐ordination numbers (strontium and barium) form 1:2 complexes also.
Rapid and efficient method for the preparation of Fmoc‐amino acids starting from 9‐fluorenylmethanol
Authors: TEN KORTENAAR PAUL B.W. , VAN DIJK BENNO G. , PEETERS J. MARJOLIJN , RAABEN BERT J. , ADAMS P.J. HANS M. , TESSER GODEFRIDUS I.
Published: August 2010

A method is presented for the high‐yield synthesis of Fmoc amino acids, which precludes racemization and over‐reaction due to carboxyl activation. A detailed procedure is given for the preparation of Fmoc‐ONSu.
Conformational and biological properties of partial sequences of salmon calcitonin
Authors: EPAND RICHARD M. , STAHL GLENN L. , ORLOWSKI RONALD C.
Published: August 2010

According to the Chou‐Fasman rules for predicting the secondary structures of proteins, the 12–20 portion of salmon calcitonin should adopt an alpha helical conformation. These residues would form an amphipathic helix and contribute to the solubilization of certain phospholipids by the peptide. Circular dichroism was used to assess the extent that peptide segments of salmon calcitonin fold into structures of higher helical content in the presence of dimyristoylphospha‐tidylglycerol, lysolecithin or sodium dodecyl sulfate. All of the segments studied are carboxyl terminal amides as is the native, intact, salmon calcitonin. Salmon calcitonin segments 11–23 or 12–23 form no more helical structure in the presence of lipids or detergents than does a segment comprising the hydro‐philic carboxyl terminal residues 22–32 which is not predicted to adopt a helical conformation. Even a larger segment containing residues 12–32 does not exhibit a great increase in helical content in the presence of lipids or detergents, and it causes only a small broadening of the phase transition of dimyristoyl‐phosphatidylglycerol. In contrast, a preparation with an equivalent molar ratio of dimyristoylphosphatidylglycerol to the salmon calcitonin segment 1–23 exhibits a very marked broadening of the phase transition, similar to what is found with the 32 amino acid native hormone. This amino terminal segment also adopts a conformation of higher helical content than even the intact hormone. This 1–23 segment is the only one studied that showed significant interaction with lipids, and it is also the only one which exhibited any hypocalcemic activity. The association constant for the binding of the 1–23 segment to dimyristoylphosphatidylglycerol is 2.4 × 104 M‐1 compared with 1.0 × 105 M‐1 for salmon calcitonin. The reduction in the affinity for lipid which occurs by removing residues 24–32 is much less than the reduction in biological activity. These and previous results indicate that the properties which give rise to lipid binding contribute to receptor affinity but are not the sole determining factor.
Synthesis and conformational study of two L‐prolyl‐L‐leucyl‐glycinamide analogues with a reduced peptide bond
Authors: ELST P. VANDER , ELSEVIERS M. , DE COCK E. , VAN MARSENILLE M. , TOURWÉ D. , VAN BINST G.
Published: August 2010

The peptide bond between Pro‐Leu or Leu‐Gly in Pro‐Leu‐Gly‐NH2 was replaced by a CH2‐NH function. The 1H and 13C n.m.r. studies demonstrated that HCl·Pro‐Leu (CH2‐NH)Gly‐NH2 10 adopted a conformation in DMSO that is similar to the previously postulated β‐turn for the natural hormone. This was not the case for the other analogue. In vivo tests on 10 revealed an activity approximately equal to the natural compound and an increased toxicity.
Simplified procedure for carrying out simultaneous multiple hydrogen fluoride cleavages of protected peptide resins
Authors: HOUGHTEN RICHARD A. , BRAY MAIREAD K. , DEGRAW STEPHEN T. , KIRBY CONNIE J.
Published: August 2010

Methods have recently been presented which greatly increase the ability to synthesize large numbers of peptides. These advances make it essential to be able to cleave large numbers of protected peptide resins. Two different procedures are presented for carrying out cleavage of protected peptide resins. The first procedure enables multiple cleavages to be carried out with many existing HF apparatuses, while the second utilizes a new apparatus design. Using these procedures, at least 50 individual cleavages can be carried out per day.
Comparison of conformational properties of proline and threonine residues
Authors: SIEMION IGNACY Z. , SOBCZYK KATARZYNA , LISOWSKI MAREK
Published: August 2010

The conformational role of Thr was investigated by 13C‐n.m.r. and CD methods using a following series of tetrapeptides: Thr‐Ala‐Ala‐Ala, Ala‐Thr‐Ala‐Ala, Ala‐Ala‐Thr‐Ala and Ala‐Ala‐Ala‐Thr. It was found that introduction of Thr in every position of the tetraalanine peptide chain distinctly influences conformational equilibria of the peptides. An increase of β‐turn forms in conformational equilibria is induced by ionization of the terminal carboxyl group, independent of threonine position in the peptide chain. Threonine in position 1 or 3 of the peptide chain seems to have some importance for β‐turn formation in acid solution.
Structure and conformation of linear peptides
Authors: MURALI R. , LALITHA V. , SUBRAMANIAN E. , PARTHASARATHY R.
Published: August 2010

The dipeptide, (DL)‐alanyl‐(DL)‐norvaline, crystallizes in the monoclinic space group P21/c, with a = 12.559(2)A, b = 5.265(1), c = 16.003(3), β = 103.53(2)°, Z = 4. The structure was solved by direct methods and refined to an R‐value of 0.054 for 871 reflections with I > 2. The molecule exists as a zwitterion in the crystal. The peptide unit is trans and shows significant deviations from planarity (Δω = 12.4°). The peptide backbone adopts an extended conformation. The unit cell contains D‐Ala‐L‐norval and its enantiomer. The molecular conformation and packing features show a striking resemblance to those for D‐Ala‐L‐Met (1), and leads to the speculation that norvaline might act as an analog of methionine.
Influence of carbamoylation on some analytical properties of basic polypeptides
Authors: LEA MICHAEL A. , LUKE ALEYKUTTY , MARTINSON CHARLES , VELAZQUEZ OMAIDA
Published: August 2010

The effect of carbamoylation on the assay or identification of histones and polylysine was investigated. Incubation with sodium cyanate decreased the positive charge on these polypeptides as judged by changes in the binding of methyl orange or the electrophoretic mobility. Histones in chromatin appeared less accessible to carbamoylation than isolated histones. Carbamoylation of proteins under conditions in which there was little or no effect on the Lowry procedure could affect their assay by methods utilizing metachromasia with Coomassie Blue G. The Bradford assay has low sensitivity for HI histone and polylysine but this can be increased by preincubation with sodium cyanate. More extensive carbamoylation of polylysine caused decreased sensitivity which was the only response seen with core nucleosomal histones and bovine serum albumin when preincubated with sodium cyanate. It was concluded that the sensitivity for HI histone and polylysine in assays dependent on metachromasia with Coomassie Blue G may be changed by factors which decrease the positive charge on these polypeptides.
The crystal structure of Boc‐Pro‐Val‐Gly‐NH2, with a remark on the conformation of the valyl residues in peptides
Authors: Ashida T. , Kojima T. , Tanaka I. , Yamane T.
Published: August 2010

The crystal structure of Boc‐Pro‐Val‐Gly‐NH2 has been determined: monoclinic; P21; a = 9.331 (3) Å, b = 9.532 (4), c = 23.080 (9), β= 91.33 (3)R, Z = 4; R = 0.053 for 3400 reflections with ˙Fo˙,>α(Fo). There are two independent but very similar molecules in the crystal. The peptide main chains are in an extended form, and packed in two kinds of antiparallel β sheets, the (φ, Φ) angles of the central Val residues are (‐156°, 146°) and (‐139°, 155°), and the mean length of the N‐ H . 0 hydrogen bonds in the sheets is 2.965 Å. A detailed study of the conformations of the Val residues in oligopeptide crystals shows that the preferred conformation of Val in peptides is: the (φ, Φ) angles close to those of the antiparallel β sheet, and Cγ1 and Cγ2, against N with respect to the Cα– Cβ bond, at either (trans, gauche) or (‐gauche, gauche). The mean π(NCαC') angle of such Val residues is 107.9(9)°. A twisting in the β sheets is also discussed.
Dehydro‐dermorphins
Authors: SALVADORI SEVERO , MARASTONI MAURO , BALBONI GIANFRANCO , MARZOLA GIULIANO , TOMATIS ROBERTO
Published: August 2010

The Phe3 and/or Tyr5 residues in dermorphin (H‐Tyr‐D‐Ala‐Phe‐Gly‐Tyr‐Pro‐Ser‐NH2) and its N‐terminal hexapeptide‐amide were replaced by Δ‐Phe or by Phe5 in order to examine the effect on opioid activity. On GPI preparation, the substitution of Phe5 for Tyr5 was well tolerated, whereas the hexa and heptapeptides containing ΔPhe in position 3 and/or 5 displayed low potency. The unsaturation at position 3 alone or at positions 3 and 5 was particularly detrimental to μ activity. In the tail flick test, the influence of unsaturation or substitution at positions 3 and 5 generally matched the results of the in vitro assay. Dehydropeptides showed comparatively low antinociceptive effects and [Phe5] analogues displayed about 50% of the analgesic potency of the original peptides.
2‐(2‘‐Pyridyl)‐ethyl‐ester (Pet ester) derivatives of polyfunctional amino acids
Authors: KESSLER HORST , BECKER GÜNTHER , KOGLER HERBERT , FRIESE JUTTA , KERSSEBAUM RAINER
Published: August 2010

The 2‐(2′‐pyridyl)‐ethyl‐esters (Pet‐esters) of bi‐ and tri‐functional amino acids are introduced as a semipermanent protecting group in peptide synthesis.
Synthesis of 14C‐labelled peptides by asymmetric reduction of dehydroamino acids*
Authors: PARNES HOWARD , SHELTON EMMA J. , HUANG GLENN T.
Published: August 2010

The labelled dehydroamino acid, 2‐N‐acetylamino‐3‐(2‐naphthyl)‐3‐[14C]‐acrylic acid was prepared at 52.8 mCi/mmol from Ba14CO3. Asymmetric reduction of this precursor with hydrogen in the presence of the chiral homogeneous catalyst (S,S) BPPMRh+ afforded N‐acetyl‐D‐3‐(2‐naphthyl)‐3‐[14C]‐alanine in greater than 98% optical yield. This unnatural amino acid was used in a solution phase synthesis of 2 14C‐labelled LHRH analogs, [N‐Ac‐D‐3‐[14C]Nal1 D‐p‐Cl‐Phe2, D‐Trp3,D‐hArg(Et2)6, D‐Ala10] LHRH and [D‐3‐[14C] Nal6] LHRH having specific activities in excess of 50 mCi/mmol.
β‐Endorphin: intranasal administration increases the serum prolactin level in monkey
Authors: RAO A. JAGANNADHA , MOUDAL N.R. , LI CHOH HAO
Published: August 2010

Human β‐endorphin has been administered by nasal spray technique at a dose of 0.02 mg per kg in female bonnet monkeys. A significant increase of serum prolactin levels was observed within 30 min and maintained up to 60 min. In the same dose, intravenous injections of the hormone caused a marginal increase of prolactin levels only after 60 min. It was concluded that administration of β‐endorphin by nasal spray is more effective than the intravenous injection.
β‐Trichosanthin: a new abortifacient protein from the Chinese drug, Wangua, Trichosanthes cucumeroides
Authors: YEUNG H.W. , LI W.W.
Published: August 2010

β‐Trichosanthin was a new abortifacient protein purified from the Chinese drug, Wangua, root tubers of Trichosanthes cucumeroides (Cucurbitaceae). The purification procedure involved acetone fractionation, ammonium sulfate precipitation, ion‐exchange chromatography on CM‐Sepharose and preparative agarose electrophoresis. Homogeneity of β‐trichosanthin was demonstrated in immunoelectrophoresis, agarose electrophoresis and SDS‐polyacrylamide gel electrophoresis. It had a molecular weight of 28 000 and no cysteine in its molecule. It differed from trichosanthin, a known abortifacient protein isolated from a related Chinese drug, Tianhuafen, root tubers of Trichosanthes kirilowii (Cucurbitaceae), in molecular weight, carbohydrate content, charge and amino acid composition. β‐Trichosanthin was, however, immunochemically identical to trichosanthin and was about twice as potent as trichosanthin in inducing mid‐term abortion in mice.
Conformation of equine pituitary somatotropin
Authors: BEWLEY THOMAS A. , LI CHOH HAO
Published: August 2010

Equine pituitary somatotropin (growth hormone) has been studied by zero‐order and second‐order absorption spectroscopy, and by circular dichroism. Difference absorption spectra have also been generated during proteolytic digestion of the hormone. The molar extinction coefficient of the native protein was found to be 16050 ± 330 M‐1 cm‐1 at 278.1 nm. Comparison of the conformations of equine somatotropin and somatotropins isolated from several other mammalian species indicates a close structural relationship between these molecules. With the increasing number of species which have been studied, it is becoming evident that with regard to conformation, the somatotropins can be subdivided into at least three major groups.
Isolation of tri‐antennary enriched and tri‐antennary depleted alpha‐1‐protease inhibitor
Authors: KARIC LUCY , GLASER CHARLES B.
Published: August 2010

Alpha‐1‐protease inhibitor, (alpha‐1‐PI), the major inhibitor of serine proteases in human plasma, has three asparagine‐linked carbohydrate chains located at positions 46, 83 and 247. The protein has a microheterogeneity which is seen on isoelectric focusing and which is a result of whether the various carbohydrate chains are in bi‐ or tri‐antennary forms. Tri‐antennary enriched forms of alpha‐1‐PI are associated with inflammation. By using a combination of three methods, reductive salting out, Sepharose‐bound Concanavalin A affinity chromatography, and Sepharose‐bound anhydrochymotrypsin, biologically active alpha‐1‐PI was obtained in tri‐antennary enriched and tri‐antennary depleted forms. These preparations should be useful for studies on the physiological role of the carbohydrate moiety in alpha‐1‐PI.
Conformation of dioxopiperazines
Authors: GDANIEC MARIA , LIBEREK BOGDAN , KOLODZIEJCZYK ALEKSANDRA S. , JANKOWSKA RENATA , CIARKOWSKI JERZY
Published: August 2010

The concept of dioxopiperazine (DOP) conformational space, according to which any conformation of the DOP ring is represented by a unique set of three orthogonal coordinates (1), is further explored. It is demonstrated that 65 DOP X‐ray conformers are distributed in their conformational space so as to produce a conformationally accessible tunnel passing through the center of the DOP conformational globe (1). The axis and an approximate shape of this tunnel are determined. The concept of the DOP conformational space is then utilized for the analysis of selected conformational preferences among the DOPs under study. From the midst of 130 amino acid residues, the component of 65 X‐ray DOP structures, at least four amino acid types emerge characterized by consistent conformational preponderances within the type. These are: (i) Pro type, contributed by 29 prolyl residues and/or its modifications in the pyrolidine ring; (ii) Phe type, composed of 33 residues with an aromatic side chain; (iii) MeAla type, contributed by 24 N‐alkylated or N‐acylated amino acid residues; and (iv) cystine type, comprising four half‐cystine residues. Both the apparent kinship and the presence of (scarce) outliers among members of a type fit established views on conformational behavior of DOPs. Utilization of the DOP conformation space has enabled us to propose the statistically most favored conformers for cyclo(Pro‐Xaa), cyclo(Phe‐Xaa), cyclo(MeAla‐Xaa) and cyclo(Cys‐Cys), where Xaa stands for an unspecified amino acid residue.
Synthesis and characterization of Tyr(Bzl)9,11,13,15 and Tyr 9,11,13,15 gramicidin A
Authors: TRUDELLE Y. , HEITZ F.
Published: August 2010

Tyr(Bzl)9,11,13,15 and Tyr9,11,13,15 gramicidin A were prepared by the solid phase method using a 4‐(oxymethyl)‐Pam resin and Bpoc as α‐amino‐protecting group. The benzylated analog [Gr.T(Bzl)] was purified by chromatography on silica gel and then on LH60 Sephadex. Removal of benzyl groups was carried out by hydrogenolysis and the debenzylated derivative (Gr.T) was purified in the same way. Both gramicidins were checked and characterized by t.l.c., HPLC, circular dichroism, 1H n.m.r. and single channel measurements. CD spectra were found to be different for Gr.T(Bzl) and Gr.T and strongly dependent upon the solvent and the concentration. Single channel conductance of Gr. T is slightly lower than that of Gr.A (A Gr.T Gr. 0.7 ˜ Gr.T).
Determination of the cleavage specificity of Streptomyces griseus protease B in the presence of guanidinium chloride
Authors: JOHNSON ERIC R. , LAMKIN REBECCA M. , JORDAN KATHERINE J. , GORDON JEFFREY A. , LINDLEY BRENDA R.
Published: August 2010

Streptomyces griseus protease B (SGPB), a Pronase enzyme, has been shown to be stable and active in the presence of 6.0 M guanidinium chloride (Siegel, S. et al. (1972) J. Biol. Chem.247, 4155–4159). In order to determine the cleavage specificity of this unusual enzyme under denaturing conditions, 12 peptides of known amino acid sequence were hydrolyzed by SGPB in the absence and presence of 6.0 M guanidinium chloride. The new N‐terminal amino acids produced by the action of SGPB were dansylated and quantitatively identified by reverse phase HPLC. The results indicate that SGPB retained its cleavage specificity for phenylalanyl, tyrosyl, tryptophanyl, and leucyl peptide bonds in the presence of 6.0 M guanidinium chloride. Of these peptide bonds, SGPB exhibited a greater cleavage preference for phenylalanyl and tryptophanyl bonds, which was relatively unaffected by the presence of the denaturant. The SGPB‐catalyzed cleavages of the leucyl peptide bonds examined (Leu‐Met, Leu‐Arg, Leu‐Val, Leu‐Thr, and Leu‐Ile) were substantially decreased under denaturing conditions, while Leu‐Gly bond cleavage by SGPB was virtually unaffected by denaturant. The demonstrated predictability of the catalytic preference of this unusual protease for phenylalanyl, tyrosyl, tryptophanyl, and leucyl‐glycine peptide bonds under denaturing conditions enhances its utility in the site‐specific proteolysis of insoluble or otherwise proteolysis‐resistant polypeptide substrates.
Influence of carboxyl groups on conformation of histone H1 from Ceratitis capitata
Authors: CABALLERO R. , FERNANDEZ B. , MONTERO F.
Published: August 2010

Salt and pH‐dependent effects on the local conformation of the two tyrosine residues of the histone H1 from the fruit fly Ceratitis capitata have been studied by difference spectroscopy, circular dichroism (CD), fluorescence emission and quenching of tyrosine emission by KI. Four different solvent conditions were used: pH 1.0 and pH 6.0 in the presence or absence of 1 M NaCl. The results clearly indicate a partial folding of the fruit fly histone H1 in the absence of NaCl upon pH increasing from 1.0 to 6.0. This folding is achieved only through ionization of acidic side chains which leads to an environment of the tyrosine residues similar to that found in salt‐folded histone H1. Furthermore, the present results give new insights into the states of the tyrosine residue responsible for the tyrosinate‐like fluorescence emission at 340 nm described previously (Jordano, J., Barbero, J.L., Montero, F. & Franco, L. (1983) J. Biol Chem.258, 315–320).
1H and 13C n.m.r. studies of pseudo‐peptide analogues of theC‐terminal tetrapeptide of gastrin
Authors: AUMELAS ANDRÉ , RODRIGUEZ MARC , HEITZ ANNIE , CASTRO BERTRAND , MARTINEZ JEAN
Published: August 2010

1H and13C n.m.r. study of pseudo‐peptide analogues of theC‐terminal tetrapeptide of gastrin, obtained by replacing each peptide bond by a “reduced peptide bond”, one at a time, e.g. Boc‐Trpø(CH2NH)Leu‐Asp‐Phe‐NH22, Boc‐Trp‐Leuø(CH2NH)Asp‐Phe‐NH23, Boc‐Trp‐Leu‐Aspø(CH2NH)Phe‐NH24, were reported. The CH2NH bond was completely characterized.1H and13C spectroscopic data were reported. It appeared from the present work that the modifications produced by the replacement of a peptide bond by a CH2NH bond were localized around the CH2NH.
Total sequential solid phase synthesis of rabbit skeletal troponin C calcium binding site III
Authors: REID R.E.
Published: August 2010

The total sequential solid phase synthesis of AcA98STnC(90–123)amide is described. The yield is comparable to that obtained previously using fragment condensation on the solid support. HPLC purification results in a product which displays greater calcium induced conformational changes than the peptide prepared by the fragment condensation method. However, the former has a dissociation constant for calcium (28 μm) seven times higher than the latter (4 μm).
Structure‐conformation relationships of synthetic peptide inhibitors of human renin studied by resonance energy transfer and molecular modeling
Authors: EPPS DENNIS E. , MAO BORYEU , STAPLES DOUGLAS J. , SAWYER TOMI K.
Published: August 2010

The structure‐conformation relationships of a series of angiotensinogen6–13 (ANG6–13, His‐Pro‐Phe‐His‐Leu‐Val‐Ile‐His) congeners substituted by Nin‐For‐Trp (Ftr), d‐Ftr or Trp at the N‐terminus, Tyr at the C‐terminus and PheΨ[CH2NH]Phe at the P1‐P′1 cleavage site (i.e. Leu10‐Val11) were studied using resonance energy transfer coupled with molecular modeling of the peptide conformation using macromolecular energy refinement and dynamics simulation. Average end‐to‐end intramolecular distances (r) of the peptides in solution were determined by fluorescence spectroscopy. For example, Ac‐Ftr‐Pro‐Phe‐His‐PheΨ[CH2NH]Phe‐Val‐Tyr‐NH2 (U‐70714E) gave an average intramolecular donor (Tyr)‐acceptor (Ftr) distance of 16.3 Å in aqueous solution. This experimental value was consistent with a distance of 17.9 Å determined by molecular modeling of U‐70714E to a human renin 3‐D structure (developed from known homologous aspartyl protease inhibitor X‐ray crystallographic data) followed by simulation of the solution phase conformation of the peptide. An extended backbone secondary structure of U‐70714E is suggested from these studies and the relationship(s) of structure‐conformation to structure‐activity was explored by analysis of several congeners of U‐70714E, a potent (IC50= 3.0 × 10−9m) inhibitor of human renin in vitro.
N‐terminal sequences of γ‐crystallins from the amphibian lens and their homology with γ‐crystallins of other major classes of vertebrates
Authors: CHIOU S.‐H. , CHANG W.‐P. , CHEN S.‐W. , LO C.‐H.
Published: August 2010

γ‐Crystallins were isolated from the homogenate of frog eye lenses (Rana catesbeiana) by exclusion gel chromatography and further purified by cation‐exchange chromatography. They were the only group of crystallins possessing free amino groups amenable to sequence analysis by Edman degradation. Comparison of the amino acid contents of the purified subfractions of γ‐crystallins indicated their close relatedness in amino acid compositions and probably sequence homology as well. The amino‐terminal sequence analysis of the purified γ‐crystallin subfractions showed extensive homology between these amphibian γ‐crystallin polypeptides themselves and also those from other vertebrate species, suggesting the existence of a multigene family and their close relatedness to γ‐crystallins of other vertebrates. The sequence comparison of the γ‐crystallin polypeptides from all major classes of vertebrates has provided strong support for the divergent evolution of γ‐crystallin family.
A β‐turn‐like conformation in “reduced” peptides Crystal structures of two dipeptide analogs with Pro‐GlyΨ[CH2‐NH] sequence
Authors: EL MASDOURI LARBI , AUBRY ANDRÉ , SAKARELLOS CONSTANTINOS , GOMEZ EMMANUEL J. , CUNG MANH T. , MARRAUD MICHEL
Published: August 2010

The conformational properties of the “reduced” dipeptides tBuCO‐Pro‐GlyΨ[CH2‐NH]NRR′(R = H, R = Et; R = R′= Me) greatly depend upon the neutral or protonated state of the “reduced” amide bond. Due to protonation, the quite flexible neutral molecule turns into a very stable conformation resembling a β‐turn in both the solid and solute states. The existence of a strong N +—H…O=C interaction closing a 10‐membered cycle illustrates the possible specific properties induced by a chemical modification in pseudopeptide analogs.
Synthesis and biological activity of [Leu5]enkephalin derivatives containing d‐glucose
Authors: HORVAT J. , HORVAT Š. , LEMIEUX C. , SCHILLER P.W.
Published: August 2010

The synthesis of some [Leu5]enkephalin derivatives is described in which d‐glucose has been linked to the opioid pentapeptide through the ester bond involving the carboxyl function at the C‐terminal with C‐1 or C‐6 of the d‐glucopyranose moiety. Enkephalin derivatives were assayed for opioid activity and found to be full agonists in bioassays based on inhibition of electrically evoked contractions of the guinea pig ileum (GPI) and of the mouse vas deferens (MVD). The obtained results suggest that the opioid activity of the tested glucoconjugates depend upon the ester bond position in the molecule. Whereas 1‐O conjugate 5 was somewhat more potent than [Leu5]enkephalin in the GPI assay, the 6‐O conjugates, with the exception of 1‐O‐benzyl derivative 11, were considerably less potent. All enkephalin derivatives were δ‐receptor selective; in particular, the acetylated analog 8 was three times more δ‐receptor selective than [Leu5]enkephalin.
Molecular conformation of alamethicin in dimethylsulfoxide solution
Authors: CHANDRASEKHAR K. , DAS MANOJ K. , KUMAR ANIL , BALARAM P.
Published: August 2010

The solution conformation of alamethicin, a 20‐residue antibiotic peptide, has been investigated using two‐dimensional n.m.r. spectroscopy. Complete proton resonance assignments of this peptide have been carried out using COSY, SUPERCOSY, RELAY COSY and NOESY two‐dimensional spectroscopies. Observation of a large number of nuclear Overhauser effects between sequential backbone amide protons, between backbone amide protons and CβH protons of preceding residues and extensive intramolecular hydrogen bonding patterns of NH protons has established that this polypeptide is in a largely helical conformation. This result is in conformity with earlier reported solid state X‐ray results and a recent n.m.r. study in methanol solution (Esposito et al. (1987) Biochemistry26, 1043‐1050) but is at variance with an earlier study which favored an extended conformation for the C‐terminal half of alamethicin (Bannerjee et al. (1983) J. Mol. Biol.165, 757‐775).
Synthetic and conformational studies on dehydrophenylalanine containing model peptides
Authors: KAUR PARAMJEET , UMA K. , BALARAM P. , CHAUHAN V.S.
Published: August 2010

Four model dipeptides containing a Z‐dehydrophenylalanine residue (ΔZPhe) at the C‐terminal, Boc‐X‐ΔZ Phe‐NHMe (X = Ala (1), Gly (2), Pro (3), and Val (4)), have been synthesised and their solution conformations investigated by 270 MHz 1H n.m.r. and i.r. spectroscopy. N.m.r. studies on these peptides clearly show the presence of intramolecularly hydrogen bonded structures in CHCl3 solutions while such structures appear to be absent in the corresponding saturated peptides. This conclusion is also supported by i.r. studies. Studies of the nuclear Overhauser effect provided evidence for the occurrence of a significant population of β‐turn structures in solvents like CDCl3 and (CD3)2SO. The observed NOES are consistent with a major contribution from Type II β‐turn structure in CDCl3, while in (CD3)2SO solutions there is evidence of a partially extended structure also.
Applications of BOP reagent in solid phase peptide synthesis III. Solid phase peptide synthesis with unprotected aliphatic and aromatic hydroxyamino acids using BOP reagent
Authors: FOURNIER ALAIN , DANHO WALEED , FELIX ARTHUR M.
Published: August 2010

The BOP reagent [benzotriazol‐1‐yl‐oxy‐tris‐(dimethylamino)phosphonium hexafluorophosphate], which has been shown to be ideally suited for solid phase synthesis, has now been found to be useful for solid phase synthesis using a minimal side‐chain protection scheme. This new application of the BOP reagent was exemplified by the successful synthesis of the CCK‐7 analog, Ac‐Tyr(SO3H)‐Met‐Gly‐Trp‐Met‐Thr(SO3H)‐Phe‐NH2, using unprotected Boc(hydroxy)‐amino acids [Boc‐Thr‐OH and Boc‐Tyr‐OH]. N‐Terminal acetylation was achieved under mild conditions by using the BOP coupling reaction with acetic acid. This procedure provided the unprotected (Tyr27, Thr32)‐peptide‐resin which is ready for the required sulfation on the solid support without selective side‐chain deprotection of Ty27 and Thr32. Solid phase sulfation was evaluated under a variety of conditions and it was determined that disulfation was optimal using pyridine acetyl sulfate (38 equiv.) in pyridine at 45° for 4 h. Shorter reaction times or milder conditions lead to the formation of the Thr32 monosulfated analog. Cleavage of the disulfated analog from the PAM‐resin was achieved using liquid ammonia and the product was purified by preparative hplc and fully characterized. The advantages of the new procedure are compared with the reported synthesis of CCK‐7.
Synthesis and biological studies of dermorphin and its analogs substituted at positions 5 and 7
Authors: SIVANANDAIAH KADLEBAL M. , GURUSIDDAPPA SIVASHANKARAPPA , BABU VOMMINA V. SURESH
Published: August 2010

Dermorphin and seven of its analogs substituted at positions 5 and/or 7, have been synthesized by the solid phase method employing mainly 9‐fluorenylmethyloxycarbonylamino acid trichlorophenyl esters in presence of 1‐hydroxybenzotriazole, the solid support being the Merrifield resin. Among the analogs synthesized, the most interesting is [Tyr7]dermorphin. It is one of the most potent dermorphin analogs reported so far. Compared to the natural peptide, it is about two times more potent in the GPI (in vitro) and nearly 1.4 times more potent in its analgesic activity in mice by the hot plate test (in vivo). Further, its antidiarrhoeal activity in mice (in vivo) is comparable to that of dermorphin. On the other hand, [Thr7]dermorphin is almost as potent as dermorphin.
Controlled proteolysis of mouse epidermal growth factor An RP‐HPLC and 1H‐n.m.r. study
Authors: MENEGATTI ENEA , SCALIA SANTO , BORTOLOTTI FABRIZIO , ASCENZI PAOLO , DE MARCO ANTONIO
Published: August 2010

Tryptic digestion of the mouse epidermal growth factor (mEGF) and the chromatographic separation of its proteolytic fragments by RP‐HPLC affords the isolation of the pure hormone, of its 1–48 (Des(49–53)mEGF) and 1–45 (Des(46–53)mEGF) derivatives, and of the carboxyl‐terminal pentapeptide W49–W50‐E51‐L52‐R53. Kinetics of mEGF proteolytic degradation follows a two‐state time‐course: native mEGF being converted into Des(49–53)mEGF with an apparent half‐time of 10min; and Des(49–53)mEGF subsequently hydrolyzed to Des(46–53)mEGF with an apparent half‐time of 7 h. Native mEGF and its proteolytic fragments have been characterized by 1H‐n.m.r. spectroscopy. In the aromatic and aliphatic regions, the 1H‐n.m.r. spectrum proved to be a sufficiently sensitive probe for following controlled proteolysis, and for analyzing the influence of the carboxyl‐terminal sequence on the hormone conformation and stability.
Conformational analysis of cyclic tetrapeptides by molecular mechanics calculations
Authors: TERADA YUKIMASA , KAWAI MEGUMI , RICH DANIEL H.
Published: August 2010

Molecular mechanics calculations of the cyclic tetrapeptide ring system for the cis, trans, cis, trans amide bond sequences for cyclo tetraglycine and cyclo tetraalanine have been carried out. A systematic search of conformational space was carried out by using Still's RINGMAKER in an attempt to find the global minimum for each amide bond sequence. Ring system structures were optimized by using the BAKMOD program. A comparison of 11 experimentally determined cyclic tetrapeptide conformations with the lowest energy calculated conformations showed that only 4 of 11 known cyclic tetrapeptides adopted the lowest energy conformation. However, when the destabilization energy between cyclo tetraalanine and cyclo tetraglycine was calculated, 10 of the 11 experimentally determined conformations for cyclic tetrapeptides with alternating cis, trans, cis, trans amide bond sequences adopted the conformations with the least de‐stabilization energy. The relationship between the molecular mechanics calculations and empirical rules for predicting cyclic tetrapeptide conformations is discussed.
Crystal structure and conformation of l‐pyroglutamyl‐l‐alanine
Authors: RAMASUBBU N. , PARTHASARATHY R.
Published: August 2010

Crystals of the dipeptide, pyroglutamyl‐alanine (C8H12N2O4) grown from aqueous methanol are monoclin‐ic, space group P21 with the following cell parameters: a = 4.863(2), b = 16.069(1), c = 6.534(2)Å and β= 109.9(2)°, V = 480.0Å3, Mr= 200.2, Dc= 1.385 g cm−3, and Z = 2. The crystal structure was solved by the application of direct methods and refined to an R value of 0.044 for 699 reflections with I > 2σ. The amide of the pyroglutamyl side chain is cis, ω1= 2.6(7)°; the peptide unit is trans and appreciably non‐planar (ω2= 167.4(5)°). The backbone torsional angles are: Ψ1= 166.1(5), φ2=−90.3(6), and Ψ2=−22.4(6)°. This structure contains a short (2.551(5)Å) intermolecular hydrogen bond between the carboxyl OH and the N‐acyl oxygen, a feature common to most acyl amino acids and acyl peptides.
Interactions of alkylureas with l‐valine, l‐valyl‐l‐valine, l‐leucine, and l‐leucyl‐l‐leucine
Authors: LAPANJE SAVO , KRANJC ZDENKA , SENEGAČNIK MARJAN M. , ŽEROVNIK EVA
Published: August 2010

The solubilities of l‐valine, l‐leucine, l‐valyl‐l‐valine, and l‐leucyl‐l‐leucine have been determined in methyl‐, N,N′‐dimethyl‐, and ethylurea solutions. Gibbs free energies of transfer of both amino acids and dipeptides as well as the peptide unit from water to alkylurea solutions have been ascertained. Enthalpies of transfer for the same compounds and the peptide unit have been determined from calorimetric measurements. The additivity principle for the contribution of the peptide unit and the side chains is obeyed neither for Gibbs free energy nor for the enthalpy of transfer. The most characteristic feature of Gibbs free energy data are the negative values for the transfer of the peptide unit to urea solutions and the positive values for the transfer to alkylurea solutions. Moreover, Gibbs free energy of transfer of the l‐valyl and l‐leucyl side chains is negative in alkylurea and urea solutions. The enthalpy of transfer values for urea solutions are generally negative, whereas the values for alkylurea solutions are positive. The enthalpy values for the l‐valyl and l‐leucyl side chains are positive as well. However, the enthalpy values for the peptide unit are all negative.
Conformations, cation binding, and transmembrane ion transfer properties of a cyclooctapeptide built by an alternation of d and l residues
Authors: HEITZ F. , KADDARI F. , HEITZ A. , RANIRISEHENO H. , LAZARO R.
Published: August 2010

The conformations of a cyclic octapeptide built with an alternation of d and l residues are investigated on the basis of 1H n.m.r. and CD data. The cyclooctapeptide can form structures which are specific to the alternating d‐l sequence. This peptide can form two types of complexes with cations (peptide2‐cation and peptide‐cation complexes) and the binding with monovalent cation is weak. This peptide is able to induce transmembrane ion transfer through both a carrier mechanism and pore formation.
Structure and conformation of peptides containing the sulphonamide junction
Authors: CALCAGNI A. , GAVUZZO E. , LUCENTE G. , MAZZA F. , POCHETTI G. , ROSSI D.
Published: August 2010

N‐acetyl‐tauryl‐l‐phenylalanine methyl ester 1 has been synthesized. The crystal structure and molecular conformation of 1 have been determined. Crystals are monoclinic, space group P21 with a = 5.088(2), b = 17.112(17), c = 9.581(6) Å, β= 92.34(4)M‐0, Z = 2. The structure has been solved by direct methods and refined to R = 0.043 for 2279 reflections with I < 1.5σ(I). The sulphonamide junction maintains the peptide backbone folded with Tau and Phe Cα atoms in a cisoidal arrangement, the torsion angle around the S‐N bond being 65.4M‐0. In this conformation the p‐orbital of the sulphonamide nitrogen lies in the region of the plane bisecting the O‐S‐O angle, thus favouring dα‐pα interactions between nitrogen and sulphur atoms. The S‐N bond with a length of 1.618 Å has significant α‐bond character. The CO‐NH is planar and adopts trans conformation. The Tau residue is extended with the Tau‐Cα1‐Cβa bond anti‐periplanar to the S‐N bond. The Phe side chain conformation corresponds to the statistically most favoured g‐ rotamer and exhibits a χ1 torsion angle of –67.5M‐0. The packing is characterized by intermolecular H‐bonds which the Tau and Phe NH groups form with the acetyl carbonyl and one of the two sulphonamide oxygens, respectively.
Conformationally restricted peptides through short‐range cyclizations
Authors: TONIOLO C.
Published: August 2010

The various types of conformationally restricted peptides obtained by short‐range cyclizations, from residueito residuei+ 1, are presented. Relevant examples of N ⇆ Cx, C′⇆ Cx, N ⇆ C′, Cx⇆ Cx, C′⇆ C′ and N ⇆ N cyclizations are reported and the pertinent literature listed. In the discussion emphasis is place on the conformational consequences for peptides from the incorporation of such ring structures.
Variation of amino acid properties in protein secondary structures, α‐helices and β‐strands
Authors: MUTHUSAMY R. , PONNUSWAMY P.K.
Published: August 2010

A study was made on the physical, chemical, energetic, conformational, geometric, and dynamic property potentials of amino acid residues in protein secondary structures: α‐helix and β‐strand. Property patterns were obtained by computing the average property values for specified residue units partitioned longitudinally and transversely about the chain. It was found that in r‐helices with not more than 15 residues, there exist longitudinally opposing portions, one characteristically higher in average property potentials than the other. The helical chain, in general, acquires either an increasing or decreasing average potential in the N‐terminal to C‐terminal direction. The sequence‐wise and surface‐wise variations of property potentials in the elements of β‐structure also revealed such general patterns. Possible wrong predictions in statistical methods of one secondary structural class over the other are pointed out.
Synthesis and characterization of 1,1,4,4‐butanetetracarboxylic acid
Authors: CABANISS S.E. , PUGH K.C. , CHARIFSON P.S. , PEDERSEN L.G. , HISKEY R.G.
Published: August 2010

1,1,4,4‐Butanetetracarboxylic acid (BTCA) is evaluated as an analogue for the metal binding site in dipeptides of γ‐carboxyglutamic acid (Gla). Molecular modeling suggests that the four carboxylic acid groups in BTCA can assume a similar conformation to the four y‐carboxylic acid groups in GlaGla and thus provides the impetus for the synthesis and metal binding determinations. BTCA is synthesized via the tert.‐butyl ester and characterized via NMR, mass spectroscopy, and elemental composition. Equilibrium binding constants with protons, Ca(II) and Mg(II) are determined via pH and Ca(II) ion‐selective electrode titrations and are found to be similar to those for GlaGla peptides with blocked termini.
Synthesis of cystine peptides 21–25/70–73 and 35–39/56–59 of the β‐subunit of human choriogonadotropin
Authors: CHATURVEDI SANJEEV , BAHL OM P.
Published: August 2010

Syntheses of two asymmetrical cystine peptides with the amino acid residues 21–25/70–73 and 35–39/56–59, based on the linear amino acid sequence and the disulfide bond assignment in the β‐subunit of human choriogonadotropin (hCG‐β), are described. S‐trityl and S‐acetamidomethyl peptide fragments of each cystine peptide were prepared in solution phase and were subjected to oxidation with I2/MeOH to form the disulfide bridge. The cystine peptides were characterized by their amino acid analyses and fast atom bombardment mass spectrometry. Immunological characterization by several homologous radioimmunoas‐say systems showed that peptide 21–25/70–73 had significant hCG, hCG‐β, and hLH activities while peptide 35–39/56–59 failed to reveal any immunoreactivity.
Protein‐polymer grafts, IV A. Modification of amino acids: IIai. Modification of free lysine with reductive arylation
Authors: KALEEM K. , CHERTOK F. , NITHIANANDAM V.S. , ERHAN S.
Published: August 2010

Inability to increase the yield of reaction between 2, 4 dihydroxybenzaldehyde and gelatin beyond 55 and 60% has led to an extensive investigation of reductive alkylation with free lysine. Even with free lysine, the extent of reaction was about 60%. Since this could be attributed to the electron donation by the phenolic hydroxyls, reductive alkylation was performed between 0‐, m‐, and p‐nitrobenzaldehydes and free lysine; 0‐ and m‐nitrobenzaldehyde were ineffective in increasing the yield while with p‐nitrobenzaldehyde a yield of 72% was achieved. The unreacted 28% of the lysines are susceptible to epichlorohydrin. These results suggest that the slow, reversible first step in reductive alkylation, the formation of the Schiff s base, is responsible for the low yield.