bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the amino acid sequence of peptides by mass spectrometry An ion notation proposal
Authors: TUINMAN ALBERT A. , PETTIT GEORGE R.
Published: August 2010

A new nomenclature is proposed that allows a precise and concise description of mass spectrometric fragments derived from peptides. The nomenclature differs from existing methods by specifically accommodating (I) extended or unusual amino acid residues, (2) cyclic‐ and cyclodepsipeptides, and (3) residues contained in branches of the main chain.
Insulin aggregation in solution
Authors: DATHE M. , GAST K. , ZIRWER D. , WELFLE H. , MEHLIS B.
Published: August 2010

The process of insulin aggregation in neutral solutions was studied by dynamic light scattering. Solutions of different concentrations were subjected to thermal and mechanical stress (37°, rotation) for a period of 4 weeks. The starting solutions contained exclusively one particle distribution of insulin in the association equilibrium with hexamers as the largest structures. After a lag period of about 8 days the solutions showed continuously increasing scattering intensities but did not evolve perceptible turbidity within the experimental period. A more rapid increase in scattering intensity was observed in diluted than in concentrated solutions. The analysis of scattering data unexpectedly revealed that insulin species did not grow continuously. After the lag period one additional relatively restricted size distribution with particles of a mean radius of about 100nm was found, the amount of which increased continuously with time. The occurrence of these particles seems to be related to adsorption phenomena of insulin to the solid interface. We assume the 100nm‐class of aggregates to be a transient state in the physical destabilization process of insulin solutions.
Complete amino acid sequence of a subunit from rapeseed high molecular weight protein
Authors: BHUSHAN R. , MAHESH V.K. , MALLIKHARJUN P.V.
Published: August 2010

A subunit (M, 15 600) from the high molecular weight protein from rapeseed was separated and isolated; its purity and homogeneity were ascertained. The subunit was cleaved with cyanogen bromide, trypsin, chymotrypsin, and Staphylococcus aureus V8 protease. The fragments were separated and isolated by polyacrylamide gel electrophoresis, gel filtration, column chromatography on Dowex 1 × 2, and paper electrophoresis. The amino acid compositions of the intact subunit and different fragments obtained from enzymatic and chemical cleavages were determined. The subunit and its fragments were sequenced by manual Edman method. The phenylthiohydantoin amino acids obtained after each step were identified by thin‐layer chromatography and ultraviolet spectroscopy. The complete amino acid sequence of the subunit consisting of 125 amino acid residues has been established by the overlapping method.
Complete amino acid sequence of goose VLDV‐neurophysin Traces of a putative gene conversion between promesotocin and provasotocin genes
Authors: MICHEL GILLES , LÉVY BRIGITTE , CHAUVET MARIE‐THÉRÈSE , CHAUVET JACQUELINE , ACHER ROGER
Published: August 2010

Goose VLDV‐neurophysin (mesotocin‐associated neurophysin) has been purified from posterior pituitary glands through molecular sieving on Sephadex G‐75 and high‐pressure reverse‐phase liquid chromatography on Nucleosil C‐18 columns. Despite apparent molecular mass of unreduced VLDV‐neurophysin measured by polyacrylamide gel electrophoresis with sodium dodecylsulfate appeared near 17kDa, this value fell to 11 kDa after reduction with mercaptoethanol, suggesting the existence of a homodimer. Complete amino acid sequence (93 residues) of goose VLDV‐neurophysin has been determined. N‐ and C‐terminal sequences of the protein have been established by Edman degradation (microsequencing) and use of carboxypeptidase Y, respectively. Peptides derived from oxidized or carboxamidomethylated neurophysin by trypsin or staphylococcal proteinase hydrolyses have been isolated by high‐pressure liquid chromatography and microsequenced, allowing determination of the complete sequence. Comparison within the vertebrate VLDV‐neurophysin lineage, namely goose VLDV‐neurophysin to mammalian VLDV‐neurophysins and to deduced toad VLDV‐neurophysin, reveals a residue insertion between positions 66 and 67 in the nonmammalian VLDV‐neurophysins. When goose MSEL‐neurophysin (vasotocin‐associated neurophysin) and goose VLDV‐neurophysin are compared to their bovine counterparts, identical substitutions are found in positions 17 (Asn in both goose neurophysins instead of Gly in both ox neurophysins), 18 (Arg instead of Lys), 35 (Tyr instead of Phe), and 41 (Thr instead of Ala). Identity of the sequences 10‐74 in both ox neurophysins has been explained by partial gene conversion between oxytocin and vasopressin genes, and identical substitutions in both goose neurophysins might reveal a similar gene conversion between mesotocin and vasopressin genes in birds.
Conformational study of cyclolinopeptide A
Authors: MORELLI M.A. CASTIGLIONE , PASTORE A. , PEDONE C. , TEMUSSI P.A. , ZANOTTI G. , TANCREDI T.
Published: August 2010

The conformation of cyclolinopeptide A, c(Pro‐Pro‐Phe‐Phe‐Leu‐Ile‐Ile‐Leu‐Val), a naturally occurring peptide with remarkable cytoprotective activity, has been investigated by means of distance geometry calculations and molecular dynamics simulations. The starting points for all the calculations were an X‐ray structure and other structures obtained from distance geometry calculations based on NMR data. Restrained and unrestrained molecular dynamics simulations are reported in vacuo and in CCI4. Structural and dynamic properties are investigated and compared with those experimentally determined. The conformation obtained from the MD simulations which best reproduces the NMR parameters is at the same time one of the most stable ones and is also fairly similar to the crystal structure. An explanation for the occurrence of multiple conformations in solution at room temperature is given.
Fully synthetic immunogens
Authors: WÜNSCH E. , MORODER L. , HÜBENER G. , MUSIOL H.‐J. , VON GRÜNIGEN R. , GÖHRING W. , SCHARF R. , SCHNEIDER C.H.
Published: August 2010

As core molecule for the multiple attachment of antigenic peptides we have selected the human IgGl hinge fragment 225–232/225′‐232′. Two types of conjugates of this double‐chain bis‐cystinyl hinge‐peptide were prepared i) by linking its C‐termini to [NIe15]‐human‐little‐gastrin‐[2‐17] and ii) by elongating the resulting hinge‐peptide/[NIe15]‐little‐gastrin‐[2‐17] conjugate at the two N‐termini with the human big‐gastrin sequence 1–14 to produce the big‐gastrin‐[l‐14]/hinge‐peptide/little‐gastrin‐[2‐17] conjugate. For the synthesis of these peptide structures both the route via the preformed double‐chain bis‐cystinyl peptide and the route via suitably protected monomeric bis‐cysteinyl peptides were used. For the latter approach advantage was taken of the previous observation about the preferred oxidation of the bis‐cysteinyl hinge‐peptide 225–232 to the dimer in parallel alignment. Both synthetic routes led to identical products. Immunization experiments in guinea pigs with the synthetic hybrids led to surprisingly strong immune responses with anti‐little‐gastrin antibody titers comparable to those induced by the iso‐I‐cytochrome c/little‐gastrin‐[2‐17] conjugate as carrier‐hapten system. These findings show that the two gastrin constructs are fully competent immunogens. Additionally, the gastrin receptor‐like specificity of the antibodies indicates that both the synthetic hybrids and the cytochrome c conjugate allow for expression of a little‐gastrin‐specific conformational epitope similar to the bioactive structure of this hormone. The usefulness of such synthetic hybrids is further confirmed by the observation that the bivalent immunogen, containing both the little‐gastrin 2–17 and the big‐gastrin 1–14 sequence, is capable of inducing an immune response against both antigenic sequences, although with different efficiency. These results fully confirm our expectations.
Two‐step hard acid deprotection/cleavage procedure for solid phase peptide synthesis
Authors: NOMIZU MOTOYOSHI , INAGAKI YOSHIMASA , YAMASHITA TAKEYOSHI , OHKUBO AKO , OTAKA AKIRA , FUJII NOBUTAKA , ROLLER PETER P. , YAJIMA HARUAKI
Published: August 2010

A new two‐step deprotection/cleavage procedure for t‐butoxycarbonyl (Boc) based solid phase peptide synthesis is reported. First the protective groups are removed from 4‐(oxymethyl)‐phenylacetamidomethyl (PAM) resin attached peptide with the weak hard acid, trimethylsilyl bromide‐thioanisole/trifluoroacetic acid (TFA). In the second step, the peptide is cleaved from the resin with a stronger hard acid such as trimethylsilvl trifluoromethanesulfonate in TFA or with HF. The method is also shown to deformylate Nin‐formyltryptophan moiety efficiently. The usefulness of this procedure for practical solid phase peptide synthesis is demonstrated by comparison with other deprotection methods in the synthesis of urotensin II and human endothelin.
Degradation of growth hormone releasing factor analogs in neutral aqueous solution is related to deamidation of asparagine residues
Authors: FRIEDMAN A. R , ICHHPURANI A. K. , BROWN D. M. , HILLMAN R. M. , KRABILL L. F. , MARTIN R. A. , ZURCHER‐NEELY H. A. , GUIDO D. M.
Published: August 2010

The incubation of a solution of the human growth hormone releasing factor analog, [Leu27] hGRF(1‐32)NH2at pH 7.4 and 37°, resulted in extensive degradation of the sample. The major degradation products were identified as the peptides [β‐Asp8, Leu27] hGRF(l‐32)NH2and [α‐Asp8, Leu27] hGRF(1‐32)NH2, produced by deamidation of the Asn8residue. When tested as growth hormone (GH) secretagogues in cultured bovine anterior pituitary cells, [β‐Asp8, Leu27] hGRF(l‐32)NH2was estimated to be 400‐500 times less potent than the parent Asn8peptide, while [2‐Asp8, Leu27] hGRF(l‐32)NH2was calculated to be 25 times less potent than the parent Asn8peptide. Three additional analogs of [Leu27] hGRF(1‐32)NH2containing either Ser or Asn at positions 8 and 28 were prepared and evaluated for their GH releasing activity and stability in aqueous phosphate buffer (pH 7.4, 37°). Based on disappearance kinetics, [Leu27] hGRF(1‐32)NH2had a half‐life of 202 h while the other analogs had the following half‐lives: [Leu27, Asn28] hGRF(1‐32)NH:(150h); [Ser8, Leu27, Asn28] hGRF(l‐32)NH2(746h); and [Ser8, Leu27] hGRF(1‐32)NH2(1550 h). After 14 days, incubated samples of the Asn8analogs lost GH releasing potency, while the Ser8analogs retained full potency. The potential for loss of biological activity brought about by deamidation of other engineered peptides and proteins should be considered in their design.
Complexation which facilitates rejoining of horse cytochrome c apofragment [Homoser‐lactone65](1‐65) or [Homoser‐lactone65] (23‐65) to apofragment (66‐104)
Authors: GOZZINI LUIGIA , TANIUCHI HIROSHI , DiBELLO CARLO
Published: August 2010

We have shown that two CNBr fragments of horse apocytochrome c, [Homoser‐lactone65](1–65) and (66–104), bind to the ferric heme fragment (1–25)H to form a non‐productive three‐fragment complex, and that when the heme of this complex has been kept reduced for 48 h at 25°, the peptide bond between residues 65 and 66 is restored with a yield of 24% or more. We have also shown that another CNBr fragment [Homoser‐lactone65](23–65), but not [Homoser‐lactone65](39–65), similarly rejoins to fragment (66–104) in the presence of the ferrous heme fragment with 25% or more yield. For complex of ferro‐heme fragment [Hse‐lacton65](1–65)H and apofragment (66–104) of horse cytochrome c, which restores the peptide bond between residues 65 and 66 (located on the left side of the heme) (cf. Harbury, H.A. (1978) in Semisynthetic Peptides and Proteins (Offord, R.E. & DiBello, C., eds.), pp. 73–89, Academic Press, New York), Corradin & Harbury have suggested that axial ligation of methionine 80 to the heme (on the left side) is important. Consistent with their idea, fragment [Hse80](66–104) was found not to link to [Hse‐lactone65](1–65) in the presence of ferro(1–25)H. Furthermore, the present studies indicate that the interaction involving residues 26 to 38 (on the right side) is also important for such a conformation which assists in the rejoining of the two apofragments. Combining these two ideas, we suggest that restoration of the peptide bond between residues 65 and 66 reflects the structural integrity of these complexes in the reduced form. Thus, the present reaction system can be used not only for chemical synthesis of [Homoser65] apocytochrome c but also to extend amino acid substitution studies of cytochrome c to residues 1 to 64.
Use of Mpc‐amino acids in solid phase peptide synthesis leads to improved coupling efficiencies
Authors: SCHIELEN WIM J.G. , ADAMS HANS P.H.M. , NIEUWENHUIZEN WILLEM , TESSER GODEFRIDUS I.
Published: August 2010

The Mpc‐group has a somewhat better stability than the Fmoc‐group, resists catalytic hydrogenolysis, is highly stable in acidic media and its elimination product does not polymerize spontaneously. In a direct comparison of coupling efficiencies obtained in solid phase peptide syntheses using Mpc‐ or Fmoc‐amino acids it is shown that the use of Mpc‐amino acids leads to better coupling efficiencies and, consequently, a more homogeneous peptide. An improved synthesis of Mpc‐ONSu and of Mpc‐amino acid derivatives is presented.
Heterodetic bicyclic decapeptide cyclo (Glu1 ‐Leu2 ‐Pro3‐Gly4‐Ser5‐Ile6‐Pro7‐Ala8) cyclo‐(1γ‐5β) Phe9‐Gly10
Authors: BARBATO GAETANO , D'AURIA GABRIELLA , PAOLILLO LIVIO , ZANOTTI GIANCARLO
Published: August 2010

Bycyclic peptides are useful model molecules that can mimic the constrained local folding of a great number of natural peptides and proteins, such as ionophoric peptides, enzyme active site, and ligand‐receptor active site. The synthesis of the bicyclic title compound with the liquid phase method is described with experimental details. Of particular interest is the heterodetic closure of the second ring. The peptide showed a complexing activity with metal cations like Ba2+, Ca2+, and Mg2+ . The free bicyclic peptide conformation in solution has been studied by means of NMR spectroscopy and a plausible structure model worked out with model building on NMR constraints is proposed.
Cyclization of disulfide‐containing peptides in solid‐phase synthesis†
Authors: ALBERICIO FERNANDO , HAMMER ROBERT P. , GARCÍA‐ECHEVERRÍA CARLOS , MOLINS M. ANTÒNIA , CHANG JANE L. , MUNSON MARK C. , PONS MIQUEL , GIRALT ERNEST , BARANY GEORGE
Published: August 2010

Disulfide‐containing peptides may be obtained in good yields and purities when oxidations are carried out on peptide chains anchored to polymeric supports used for solid‐phase synthesis. Such approaches take advantage of the pseudo‐dilution phenomenon which favors intramolecular processes. A variety of procedures have been demonstrated using the related model peptides Ac‐Cys‐Pro‐d Val‐Cys‐NH2 and Ac‐Pen‐Pro‐d Val‐Cys‐NH2 (which both readily assume a type II β‐turn conformation that becomes stabilized by a 14‐membered disulfide‐containing intramolecular ring), and oxytocin (conformationally mobile 20‐membered disulfide ring). Both Boc and Fmoc were used for Nα‐amino protection, the β‐thiols of cysteine or penicillamine were blocked by S‐acetamidomethyl (Acm), S‐9‐fluorenylmethyl (Fm), or S‐trityl (Trt), and compatible anchoring linkages included HF‐labile 4‐methylbenzhydrylamide (MBHA), TFA‐labile tris (alkoxy)benzylamide (PAL), and photolabile o‐nitrobenzylamide (Nonb). Assemblies of linear sequences proceeded smoothly, and polymer‐supported oxidations were carried out in a variety of ways either directly or after deblocking to the resin‐bound dithiol. Chains were released from the support without substantial damage to the disulfide bridges, and overall yields were as high as 60‐90%.
Determination of the disulfide bond pairings in bovine transforming growth factor‐α
Authors: VIOLAND BERNARD N. , TOU JACOB S. , VINEYARD BILLY D. , SIEGEL NED R. , SMITH CHRISTINE E. , PYLA PAUL D. , ZOBEL JAMES F. , TOREN PAUL C. , KOLODZIEJ ERIC W.
Published: August 2010

A rapid method for determining the three disulfide bond pairings in bovine transforming growth factor‐α (bTGF‐α) was developed by digesting bTGF‐α with thermolysin followed by separation of the generated peptides by reversed‐phase HPLC. The disulfide‐bonded peptides were identified by amino acid sequencing and fast atom bombardment mass spectrometry. The disulfide bond pairings in bTGF‐α were determined to be homologous to those in the human and mouse TGF‐α molecules. A species of low bioactivity isolated from the folding/oxidation mixture of chemically synthesized bTGF‐α was demonstrated to contain two incorrect disulfide bonds. These results indicate that mispairing of disulfide bonds in bTGF‐α significantly reduces the activity of this molecule.
Synthesis of S‐alkyl and C‐terminal analogs of the Saccharomyces cerevisiae a‐factor
Authors: XUE CHU‐BIAO , BECKER JEFFREY M. , NAIDER FRED
Published: August 2010

The a‐mating factor of Saccharomyces cerevisiae, Tyr‐Ile‐Ile‐Lys‐Gly‐Val‐Phe‐Trp‐Asp‐Pro‐Ala‐Cys(far‐nesyl)OCH3, and 10 analogs modified at the cysteine side chain and/or the terminal carboxyl were synthesized using a combination of solid phase and solution phase methodologies. The strategy of synthesis involved the condensation of an amine terminal protected decapeptide with a carboxyl terminal S‐alkylated dipeptide ester or amide using benzotriazoI‐1‐yloxy‐tris(dimethylamino)‐phosphonium hexafluoro‐phosphate as the coupling agent. The protected decapeptide was assembled on a PAM‐resin using 9‐fluorenylmethoxycarbonyl (Fmoc) for the protection of the Tyr α‐amine and Lys ω‐amine and 9‐fluorenyl‐methyl ester (OFm) for the protection of the Asp β‐carboxyl. Premature loss of the OFm group from the HF cleavage was observed at 0‐2°, whereas no loss occurred when the cleavage reaction was conducted at – 5°. In contrast to these results, the OFm group in Asp(OFm) was partially removed by HF at – 5° and was completely stable to HF only at – 20°. The S‐alkylated dipeptide esters were prepared, in yields from 64% to 88%, via thioalkylation of amine protected or unprotected dipeptide esters using potassium fluoride dihydrate as the base. The use of a tertiary amine as the base for thiohexadecanylation resulted in low reactivity.
Cyclization studies with tetra‐and pentapeptide sequences corresponding to β‐casomorphins
Authors: SCHMIDT RALF , NEUBERT KLAUS
Published: August 2010

The tetrapeptide Boc‐d‐Orn‐Phe‐d‐Pro‐Gly‐OH and the pentapeptide sequence Boc‐Tyr(tBu)‐d‐Orn‐Phe‐d‐Pro‐Gly‐OH were used to study the influence of different coupling reagents on the yield and purity of these model peptides. The simple structure prevented racemization and cyclodimerization and facilitated the ring formation. The most favorable effects on yield and purity were obtained in both reactions using diphenylphosphoryl azide (DPPA) and norborn‐5‐ene‐2,3‐dicarboximidodiphenylphosphate (NDPP), while the cyclizations with the powerful activating reagents benzotriazol‐l‐yl‐oxy‐tris(dimethylamino)‐phosphonium hexafluorophosphate (BOP) and 2‐(1‐H‐benzotriazol‐l‐yl)‐1,1,3,3‐tetramethyluronium hexafluorophosphate (HBTU) with the exception of the cyclopentapeptide reaction with HBTU/4‐dimethylaminopyridine gave unsatisfactory results.
Evidence for a glycoconjugate form of glutathione S‐transferase pI
Authors: KUZMICH SANDRA , VANDERVEER LISA A. , TEW KENNETH D.
Published: August 2010

The anionic form of glutathione S‐transferase from human (GST) and rat (GSTYp) sources has been shown to exist in multiple forms which have similar molecular weights but different isoelectric points (pIs). Treatment with endoglycosidase H caused the acidic forms of GST Yp to be converted to proteins with more basic pIs as compared to the untreated control mixtures, suggesting that an N‐linked mannose moiety containing acidic residues had been removed. Inability to detect these carbohydrates by techniques requiring unsubstituted vicinal hydroxyls further suggested acidic substitutions on the sugar moiety. GST/Yp carbohydrate modifications were also identified by differential staining procedures. These data represent the first indication that glycosylation of GST can occur. Additionally, this may offer an explanation for the often seen microheterogeneity within a class of GST isozymes.
Oxytocin antagonists with changes in the Asn5position shed light on hormone‐oxytocin receptor interactions
Authors: HILL PATRICIA S. , CHAN W. Y. , HRUBY VICTOR J.
Published: August 2010

Since oxytocin agonists and antagonists have different structure‐activity relationships, we have investigated the stereostructural and stereoelectronic requirements of the Asn5residue in oxytocin antagonists by the synthesis of four analogues of the potent, prolonged acting oxytocin antagonist [Pen1,d‐Phe2,Thr4,Orn8]‐oxytocin (I) in which Asn5was replaced respectively with Thr (II), Leu5(III), Asp5(IV) and Tyr5(V). These analogues had pA2values in the antioxytocicin vitrorat uterine assay of 7.23 (I), 7.16 (II), 6.67 (III), 7.21 (IV), and 6.76 (IV), respectively. All were also found to be weakly potent in thein vivoanti‐vasopressor assay in the rat. These studies demonstrate very different structural and stereoelectronic requirements for oxytocin agonists and antagonists when they interact with the oxytocin uterine receptor.
Chemical modification of human growth hormone with N‐acetylimidazole
Authors: KALIMAN PERLA , ERMÁCORA MARIO R. , NOWICKI CRISTINA , WOLFENSTEIN‐TODEL CARLOTA , SANTOMÉ JOSÉ A.
Published: August 2010

The effect of acetylation of tyrosine residues on the binding capacity of human growth hormone (hGH) to rat liver lactogenic and somatogenic receptors was studied. When 3.7 tyrosine and 4.8 lysine residues were acetylated with N‐acetylimidazole, both the in vivo and the in vitro capacities of hGH to compete with 125I‐labeled bovine growth hormone for somatogenic binding sites greatly decreased. Acetylation also affected the in vitro binding capacity to lactogenic sites. Most of the somatogenic binding activity was recovered by hydroxylamine treatment, which removes O‐acetyl groups from tyrosine residues but not N‐acetyl groups from lysine residues. The same treatment partially restored lactogenic binding capacity. The reactivity of hGH tyrosine residues to N‐acetylimidazole, together with previous evidence, suggests that: (a) Tyrosine residues 160 and 164, when acetylated, are likely to be responsible for the low binding activity of acetylated hGH. (b) Tyrosine 160 may play a significant role in hGH interaction with lactogenic receptors.
A synthetic peptide corresponding to a sequence in the GTPase activating protein inhibits p21ras stimulation and promotes guanine nucleotide exchange
Authors: RUBINFELD BONNEE , WONG GAIL , BEKESI EVA , WOOD ALEXANDER , HEIMER EDGAR , McCORMICK FRANK , POLAKIS PAUL
Published: August 2010

Amino acid sequence homology between the GTPase Activating Protein (GAP) and the GTP‐binding regulatory protein, Gsα, suggests that a specific region of GAP primary structure (residues 891–898) may be involved in its stimulation of p21ras GTP hydrolytic activity (McCormick, F. [1989] Nature340, 678–679). A peptide, designated p891, corresponding to GAP residues 891–906 (M891RTRVVSGFVFLRLIC906) was synthesized and tested for its ability to inhibit GAP‐stimulated p21ras GTPase activity. At a concentration of 25 μm, p891 inhibited GAP activity approximately 50%. Unexpectedly, p891 also stimulated GTP binding to p21N‐ras independent of GAP. This stimulation correlated with an enhancement of p21N‐ras GDP dissociation; an approximate 15‐fold increase in the presence of 10 μm p891. In contrast, dissociation of the p21N‐ras GTPγS complex was unaffected by 10μM p891. The p21N‐ras GDP complex was unresponsive to 100μM mastoparan, a peptide toxin shown previously to accelerate GDP dissociation from the guanine nucleotide regulatory proteins, Gi and Go. p21H‐ras, as well as the two p21H‐ras effector mutants, Ala‐38, and Ala‐35, Leu‐36, also exhibited increased rates of GDP dissociation in the presence of p891. Also tested were three ras‐related GTP‐binding proteins; rap, G25K and rac. The rap GDP complex was unaffected by 10 μm p891. Dissociation of the G25K‐ and rac GDP complexes were enhanced slightly; approximately 1.3‐and 1.8‐fold over control, respectively. Thus, the inhibitory effect of p891 on GAP stimulation of p21ras suggests that amino acids within the region 891–906 of GAP may be essential for interaction with p21ras. In addition, p891 independently affects the nucleotide exchange properties of p21ras.
Synthesis and receptor binding activity of elephant β‐endorphin, a β‐endorphin homolog with highly potent analgesic activity#
Authors: CHENG HEUNG‐CHIN , YAMASHIRO DONALD
Published: August 2010

Elephant β‐endorphin and its analog, elephant β‐endorphin(6‐31) were synthesized by standard solid phase method. Receptor binding activity showed that elephant β‐endorphin was five to six times more potent than human β‐endorphin in its ability to bind to opiate receptors on rat brain membrane. In a previous study (Wong, C.‐L., Wai, M.‐K., Cheng, H.‐C., Chung, D. & Yamashiro, D (1990) Clinical and Experimental Pharmacology and Physiology16, 33–37), tail flick test for intracerebroventricularly administered β‐endor‐phin showed that the antinociceptive potency of elephant β‐endorphin was seven to eight times higher than that of human β‐endorphin in mice. Results from both studies suggest that elephant β‐endorphin was a much more potent antinociceptive agent than human β‐endorphin in tail flick test and its higher analgesic activity might be due to its higher affinity for opiate receptors in the brain.
Synthesis of redox derivatives of lysine and related peptides containing phenothiazine or tris(2,2′‐bipyridine)ruthenium(II)
Authors: PEEK BRIAN M. , ROSS GLENN T. , EDWARDS STEPHEN W. , MEYER GERALD J. , MEYER THOMAS J. , ERICKSON BRUCE W.
Published: August 2010

Boc‐l‐Lysine derivatives and lysine‐containing peptides bearing the electron donor 10H‐phenothiazine (PTZ) or the redox chromophore tris(2,2′‐bipyridine)ruthenium(II) dication ([Rub3,]2H, where b is 2,2‐bipyridine) have been synthesized and characterized. SeO2 oxidation (53% yield) of 4,4′‐dimethyl‐2,2′‐bipyridine, Ag2:O oxidation (85% yield) of the monoaldehyde, complexation (96% yield) of 4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic acid (m‐OH) with Rub2Cl2:. activation (81% yield) of the acid [Rub2m‐OH]2+ (PF6−)2, and condensation (83% yield) of the succinimido ester [Rub2m‐OSu]2+ (PF6−)2 with Boc‐Lys furnished the protected redox‐chromophore module [Boc‐Lys(Rub2m)‐OH]2+(PF6−)2 in 29% overall yield over five steps. The first two steps constitute the first practical synthesis of the monocarboxylic acid m‐OH (45% overall yield). Also prepared were m‐OSu, Boc‐Lys(m)‐OH, Boc‐Lys(m)‐OCH3, and [Rub2m‐NHCH3]2+ (PF6−)2:. Activation (91% yield) of 3‐(10H‐phenothiazine‐10)propanoic acid (PTZpn‐OH) and condensation (92% yield) of the succinimido ester PTZpn‐OSu with Boc‐Lys furnished the protected electron‐donor module Boc‐Lys(PTZpn)‐OH (84% overall yield). The latter was used in solid‐phase syntheses of two redox tripeptides. CH3CO‐Ala‐Lys(PTZpn)‐Ala‐OH and [Rub2m‐Ala‐Lys(PTZpn)‐Ala‐OH]2 (PF6−)2. The electrochemical properties of these redox amino acids and peptides were similar to those of PTZpn‐OH, [Rub2 m‐OH]2+(PF6)2. or [Rub2 m‐NHCH3]2+ (PF6−)2. Lys(PTZpn). [Lys(Rub2m)]2+ (PF6)2:. and other redox modules may be useful for engineering light‐harvesting proteins, photovoltaic cells, and other molecular electronic devices.
Cleavage kinetics and anchor linked intermediates in solid phase peptide amide synthesis
Authors: DÜRR HANSJÖRG , BECK‐SICKINGER ANNETTE G. , SCHNORRENBERG GERD , RAPP WOLFGANG , JUNG GÜNTHER
Published: August 2010

Kinetics and cleavage conditions of peptide amide synthesis were studied using the anchor molecules 5‐(4′‐aminomethyl‐3′,5′‐dimethoxyphenoxy)valeric acid (4‐ADPV‐OH) and 5‐(2′‐aminomethyl‐3′,5′‐dimethoxyphenoxy)valeric acid (2‐ADPV‐OH). Unexpectedly the anchor amide alanyl‐4‐ADPV‐NH2 was isolated and characterized as an intermediate during the cleavage with trifluoroacetic acid (TFA) of alanyl‐4‐ADPV‐alanyl‐aminomethyl‐polystyrene to yield the alanine amide. As a matter of fact the NH–CHα bond of the alanyl spacer has to be cleaved to form this intermediate. Using TFA‐dichloro‐methane (1:9) alanyl‐4‐ADPV‐NH2 was obtained as a cleavage product in 50% yield within 60min, whereas the isomeric alanyl‐2‐ADPV‐NH2 was formed more slowly under these mild conditions. At high TFA concentration no difference between the 2‐ and 4‐ADPV anchor was observed in the rate of formation of the free alanine amide. The presence of tryptophan amide in the cleavage mixture resulted in an anchor alkylated tryptophan amide, which remains stable in acidic solution but disappears rapidly in the presence of the resin. A low TFA/high TFA cleavage procedure is recommended for peptide amid synthesis applying the ADPV anchor.
Some pharmacological properties of cyclic and linear analogs obtained by substituting each residue of an oxytocin antagonist with d‐tryptophan
Authors: FLOURET GEORGE , BRIEHER WILLIAM , MAJEWSKI TADEUSZ , MAHAN KEVIN , WILSON LAIRD
Published: August 2010

We synthesized 10 analogs (1–10) derived from the sequence of [Pmp1, D‐Trp2, Arg8]oxytocin, (parent antagonist or PA), (Pmp =β,β‐pentamethylene‐β‐mercaptopropionic acid) which is a potent antagonist (pA2= 7.77) of the uterotonic effect of oxytocin (OT) in rats, as determined in our uterotonic assay. Eight of the following analogs were designed by replacement of each residue in the PA sequence, other than the residue at position 2, with d‐tryptophan: Ac‐d‐Trp‐d‐Trp‐Ile‐Gln‐Asn‐Val‐Pro‐Arg‐Gly‐NH2, (1); [Pmp1, d‐Trp(For)2, Arg8] OT, (2); [Pmp1, d‐Trp2, d‐Trp3, Arg8] OT, (3); [Pmp1, D‐Trp2, d‐Trp4, Arg8] OT, (4); [Pmp1, d‐Trp2, d‐Trp5, Arg8] OT, (5); Aaa‐d‐Trp‐Ile‐Gln‐Asn‐d‐Trp‐Pro‐Arg‐Gly‐NH2, (6); [Pmp1, d‐Trp2, d‐Trp7, Arg8] OT, (7); [Pmp1, d‐Trp2, d‐Trp8] OT, (8); [Pmp1, d‐Trp2, Arg8, d‐Trp9] OT, (9); [Pmp1d‐Trp2, Arg8, d‐Trp(For)9] OT, (10). To avoid free mercaptan groups, Val6 was chosen in analog 1 instead of Cys and Aaa1 (Aaa = 1‐adamantaneacetic acid) in analog 6 instead of Pmp1. Of the linear analogs, 1 was inactive as an OT antagonist and 6 was a very poor antagonist, with a pA2= 5.66, but it was more potent than Aaa‐d‐Trp‐Ile‐Gln‐Asn‐Val‐Pro‐Arg‐Gly‐NH2, which has a pA2= 5.33, as we had previously reported. Analog 2, featuring d‐Trp(For)2, pA2= 7.37, was weaker than PA, indicating that the formyl group lowers potency. Analogs 3 and 4 were much weaker than PA, and analog 5 was inactive. Hence, other than at position 2, d‐Trp is undesirable in the ring sequence of PA. However, analogs featuring d‐substituents in the tail portion of PA were good antagonists. Replacement with d‐Trp7 gave antagonist 7, pA2= 7.92, which is somewhat more potent than PA. Replacement with d‐Trp9 gave antagonist 9, pA2= 8.18, which is about 2.5 times more potent than PA, although d‐Trp(For)9, introduced in analog 10, pA2= 8.10, was not as potent. Replacement with d‐Trp8 results in analog 8, pA2= 7.83, equipotent with PA. In the antidiuretic assay analogs 7, 8, and 9, each with a pA2 equal to or less than < 5.6, were very weak antagonists of the antidiuretic hormone, arginine vasopressin (AVP). Hence, the potent analogs 7, 9, and especially 8 which, unlike AVP or the usual OT antagonists, lacks a basic amino acid, are important leads for future design of highly potent and probably, more selective OT antagonists.
[Hyp3]‐tuftsin ([Hyp3]‐TU) synthesis and biological activity
Authors: GALASIK‐BARTOSZEK URSZULA , KONOPIKA DANUTA , PLECH ANDRZEJ , NAJJAR VICTOR A. , BRUS RYSZARD
Published: August 2010

[Hyp3]‐tuftsin (Thr‐Lys‐Hyp‐Arg) has been synthesized by the liquid‐phase method. In biological investigations performed on rats antinociceptive and diuretic effects have been determined. It has been suggested that the presence of hydroxyl substituent in pyrrolidine ring of proline slightly modifies antinociceptive TU effect and is responsible for the increased diuretic [Hyp3]‐TU activity.
Vibrational circular dichroism spectra of unblocked proline oligomers
Authors: DUKOR RINA K. , KEIDERLING TIMOTHY A. , GUT VLADIMIR
Published: August 2010

Vibrational Circular Dichroism (VCD) spectra of unblocked l‐proline oligopeptides, (Pro)n n = 3 to 7, dissolved in D2O are reported. For these oligomers, the VCD spectra can be attributed to a conformational dominance of the trans amide conformation with subunits interrelated by a left‐handed twist, particularly for the longer oligomers. As a function of oligomer length, formation of this conformation starts at n = 3; and by n = 5 a spectrum closely resembling that of the poly‐l‐proline II helix in shape and magnitude is seen. The VCD data are compared with previous (Pro)n results using IR, CD, Raman and NMR spectroscopies, and reasons for the variations in interpretation are discussed.
Molecular properties of poly(RGD) and its binding capacities to metastatic melanoma cells
Authors: MURATA JUN , SAIKI IKUO , OGAWA RYU , NISHI NORIO , TOKURA SEIICHI , AZUMA ICHIRO
Published: August 2010

We examined the binding capacity of anti‐metastatic polypeptide containing repetitive Arg‐Gly‐Asp(RGD) sequence derived from cell binding site of fibronectin, poly(RGD), to the surface of tumor cells. Poly(RGD) competitively inhibited the binding of radiolabeled fibronectin to the cell surface more potently than oligo(RGD) or RGD tripeptide on a molar basis. Compared on a weight basis to oligo(RGD) or RGD peptide, poly(RGD) was more active than the oligo‐ and monomeric peptide at inhibiting tumor cell adhesion to immobilized fibronectin. The secondary structure of poly(RGD) was predicted to be a β‐turn from the data of CD spectra and its amino acid sequence. These findings suggest that poly(RGD)‐mediated inhibition of cell adhesion is due to its potent binding capacity to fibronectin receptors on cell surface probably through its conformational properties.
How can the aromatic side‐chains modulate the conductance of the gramicidin channel? A new approach using non‐coded amino acids
Authors: DAUMAS PASCAL , BENAMAR DRISS , HEITZ FRÉDÉRIC , RANJALAHY‐RASOLOARIJAO LAURENT , MOUDEN RADOUANE , LAZARO RENÉ , PULLMAN ALBERTE
Published: August 2010

In order to elucidate the role of the aromatic side‐chains in the mechanism of transduction of monovalent cations through the channel of linear gramicidin, two series of analogues containing non‐coded aromatic amino acids were synthesized. In the first series, the four tryptophans were replaced by either four l‐3‐(8‐quinolyl)alanyl or four l‐3‐(4‐quinolyl)alanyl residues and single channel conductance measurements showed that these substitutions led to a strong lowering of the channel conductance, which is attributed to a modification of the orientation of the aromatic side‐chains due to an increase of their hydrophobicity. In the second series, the analogues contained both tryptophyl and naphthylalanyl residues in various amounts and positions. The single channel conductance data indicated that the conductance was mainly governed by the number of polar residues (Trp) and not by their positions. The conformational consequences of these results are discussed together with their influence on the energy profile of the gramicidin channel.
Synthesis of a potent agonist of substance P by modifying the methionyl and glutaminyl residues of theC‐terminal hexapeptide of substance P
Authors: KARAGIANNIS KOSTAS , MANOLOPOULOU AMALIA , STAVROPOULOS GEORGE , POULOS CONSTANTINE , JORDAN CHRISTOPHER C. , HAGAN RUSSELL M.
Published: August 2010

Analogues of [Orn6]‐SP6‐11have been synthesized in which the Met11residue is replaced by glutamate γ‐alkylesters. These analogues were tested in threein vitropreparations representative of NK‐1, NK‐2, and NK‐3 receptor types. Substitution of the SCH3group of the Met11side chain by a COOR (R = methyl, ethyl, n‐propyl, n‐butyl, cyclohexyl) group results in analogues which are full agonsists in NK‐1 and NK‐2 preparations but show little agonist activity in the NK‐3 preparation. When the SCH3group is replaced by a t‐butyl ester group and the resulting analogue is a full agonist in all the above preparations and more active than the parent hexapeptide and SP‐OCH3at NK‐1 receptors. It is concluded that for activity at NK‐1 receptors methionine can be replaced by γ‐t‐butyl glutamate without loss of activity, whilst at NK‐2 and NK‐3 receptors the above substitution increases the activity of [Orn6]‐SP6‐11. Other γ‐alkyl esters of the glutamic acid reduce its biological activity.
Synthesis of homologous peptides using fragment condensation: analogs of an HIV proteinase substrate
Authors: BLÁHA IVO , NEMEC JOSEF , TÖZSÉR JÓZSEF , OROSZLAN STEPHEN
Published: August 2010

Two protected peptides Boc‐Val‐Ser(Bzl)‐Gln‐Asn‐Tyr(BrZ)OH and Boc‐Val‐Ser(Bzl)‐Gln‐Asn‐Tyr(BrZ)‐ProOH were synthesized on a resin substituted by 9‐(hydroxymethyl)‐2‐fluoreneacetic acid. After cleavage with piperidine/DMF, desalting, and activation, these peptides were used for the synthesis of 11 analogs of an HIV proteinase nonapeptide substrate Val‐Ser‐Gln‐Asn‐Tyr‐Pro‐Ile‐Val‐Gln‐NH2 using fragment condensation in solid phase. The fragment condensation was made in an ultrasonic bath. Using only 2 equivalents of the activated peptide in a DMF solution, this reaction was complete in 2h. All nonapeptides were assayed as substrates for HIV‐1 and HIV‐2 proteinases.
Glycosylation of synthetic peptides breaks helices
Authors: OTVOS LASZLO , THURIN JAN , KOLLAT EMMA , URGE LASZLO , MANTSCH HENRY H. , HOLLOSI MIKLOS
Published: August 2010

Two proposed glycosylation sites are located within T cell epitopes of rabies virus glycoprotein, namely VVEDEGCTNLSGF (VF13; amino acids 29‐41) and GKAYTIFNKTLM (GM12; amino acids 312‐323). To explore the effects on peptide conformation due to post‐translational modifications, we synthesized glycosylated and phosphorylated versions of the two peptides and compared their structures with the native peptide using CD and FT‐IR spectroscopy. After the modifications, i.e., glycosylation on Asn with one or two N‐acetyl‐glucosamine or glucose residues or phosphorylation on Ser, the low to medium degree of helicity of the unmodified peptides disappears as indicated by CD measurements in water‐trifluoroethanol mixtures. Incorporation of one sugar moiety into either peptide resulted with a high probability in a type I (III) β‐turn formation with almost identical spectra for the different peptides. Elongation of the carbohydrate in GM12 only slightly enhanced this effect. In contrast, phosphorylation of VF13 caused distorted conformation of the peptide backbone. This novel and direct demonstration of a change in secondary structure by glycosylation (or phosphorylation) might be an important element in determining peptide antigen structure and function.
Stereochemistry of peptides containing 1‐aminocycloheptane‐1‐carboxylic acid (Ac7c)
Authors: VALLE G. , CRISMA M. , TONIOLO C. , SUDHANAND  , RAO R. BALAJI , SUKUMAR M. , BALARAM P.
Published: August 2010

The crystal structures of four peptides incorporating l‐aminocycloheptane‐l‐carboxylic acid (Ac7c) are described. Boc‐Aib‐Ac7c‐NHMe and Boc‐Pro‐Ac7c‐Ala‐OMe adopt β‐turn conformations stabilized by an intramolecular 4 × 1 hydrogen bond, the former folding into a type‐I/III β‐turn and the latter into a type‐II β‐turn. In the dipeptide esters, Boc‐Aib‐Ac7c‐OMe and Boc‐Pro‐Ac7c‐OMe, the Ac7c and Aib residues adopt helical conformations, while the Pro residue remains semi‐extended in both the molecules of Boc‐Pro‐Ac7c‐OMe found in the asymmetric unit. The cycloheptane ring of Ac7c residues adopts a twist‐chair conformation in all the peptides studied. 1H‐NMR studies in CDCl3 and (CD3)2SO and IR studies in CDCl3, suggest that Boc‐Aib‐Ac7c‐NHMe and Boc‐Pro‐Ac7c‐Ala‐OMe maintain the β‐turn conformations in solution.
Solid phase synthesis of partially protected and free peptides containing disulphide bonds by simultaneous cysteine oxidation‐release from 2‐chlorotrityl resin
Authors: BARLOS KLEOMENIS , GATOS DIMITRIOS , KUTSOGIANNI SOPHIA , PAPAPHOTIOU GEORGIOS , POULOS CONSTANTINE , TSEGENIDIS THEODORE
Published: August 2010

The disulphide bridge‐containing protected peptides calcitonin (1‐10) and (Tyr1)‐somatostatin‐14 were obtained in good yields and high purity by simultaneous iodine oxidation of Cys (Trt) residues and release of the protected peptides from 2‐chlorotrityl resin.
Crystal and molecular structure of l‐valyl‐l‐lysine hydrochloride
Authors: YENNAWAR HEMANT P. , NATARAJAN S. , VISWAMITRA MA.
Published: August 2010

l‐Valyl‐l‐lysine hydrochloride, C11N3O3H23 HCl, crystallizes in the monoclinic space group P2, with a = 5.438(5), b = 14.188(5), c = 9.521(5) Å, β= 95.38(2)° and Z = 2. The crystal structure, solved by direct methods, refined to R = 0.036, using full matrix least‐squares method. The peptide exists in a zwitterionic form, with the N atom of the lysine side‐chain protonated. The two γ‐carbons of the valine side‐chain have positional disorder, giving rise to two conformations, χ111= ‐67.3 and 65.9°, one of which (65.9°) is sterically less favourable and has been found to be less popular amongst residues branching at β‐C. The lysine side‐chain has the geometry of g− tgt, not seen in crystal structures of the dipeptides reported so far. Interestingly, χ32 (63.6°) of lysine side‐chain has a gauche+ conformation unlike in most of the other structures, where it is trans. The neighbouring peptide molecules are hydrogen bonded in a head‐to‐tail fashion, a rather uncommon interaction in lysine peptide structures. The structure shows considerable similarity with that of l‐Lys‐l‐Val HO in conformational angles and H‐bond interactions [4].
Use of hydrophilic diamines for bridging of two opioid peptide pharmacophores
Authors: STEPINSKI JANUSZ , ZAJACZKOWSKI IGNACY , KAZEM‐BEK DYMITR , TEMERIUSZ ANDRZEJ , LIPKOWSKI ANDRZEJ W. , TAM S. WILLIAM
Published: August 2010

The bivalent ligand approach, which assumes that two pharmacophores are connected by a spacer, was used to design receptor type‐selective ligands for opioid receptors. The first two opioid peptide bivalent ligands with different spacer lengths containing different numbers of hydroxyl groups, (Tyr‐d‐Ala‐Gly‐Phe‐NH‐CH2‐CHOH‐)2and (Tyr‐d‐Ala‐Gly‐Phe‐NH‐CH2‐CHOH‐CHOH‐)2, were synthesized and their binding to mu, delta, and kappa opioid receptors was characterized. Both analogues were found to possess high opioidin vitroactivities. The length of the hydrophilic spacer does not affect the affinity for delta receptors, whereas shorter spacer length increases affinity for mu and even more so for kappa receptors. Thus receptor type‐selective peptides for opioid receptors can be designed using the bivalent approach.
Novel version of Multiple Antigenic Peptide allowing incorporation on a cysteine functionalized lysine tree
Authors: BALEUX F. , DUBOIS P.
Published: August 2010

A novel version of Multiple Antigenic Peptide (MAP) is described. This approach consists of the synthesis of a properly functionalized antigen carrier and the incorporation, on request, of one or more activated antigenic peptides. This method was to synthesize a MAP containing eight epitopes of Hsp 70‐1 from Plasmodium falciparum. Mice immunised with this MAP gave a specific response while those immunised with the peptide alone did not.
Application of arylsulphonyl side‐chain protected arginines in solid‐phase peptide synthesis based on 9‐ fluorenylmethoxycarbonyl amino protecting strategy
Authors: FISCHER PETER M. , RETSON KIM V. , TYLER MARGARET I. , HOWDEN MERLIN E.H.
Published: August 2010

One of the main problems still hampering solid‐phase peptide synthesis using orthogonal protection strategies based on the 9‐fluorenylmethoxycarbonyl amino protecting group is the difficult removal of currently used arginine arylsulphonyl guanidino protecting groups. Poor acid lability of 4‐methoxy‐2,3,6‐trimethylbenzenesulphonyl‐protected arginine has led to the popularity of the newer 2,2,5,7,8‐pentamethylchroman‐6‐sulphonyl guanidino protecting group. This group was initially believed to have lability to trifluoroacetic acid, the reagent commonly used to simultaneously deprotect peptides and detach them from the synthesis resin, comparable to tert.‐butyl and trityl type protecting groups used for the protection of other peptide side‐chain functionalities. In a comparison of three established cleavage/deprotection mixtures we have shown that this is not always the case, particularly in multiple arginine peptides. We have found that only hard‐acid deprotection with trimethylsilyl bromide reliably removed both arylsulphonyl guanidino protecting groups from a variety of arginine‐containing peptides.
Ethylcarbamoyl protection for cysteine in the preparation of peptide‐conjugate immunogens
Authors: BLAKE JAMES , WOODWORTH BECKY A. , LITZI‐DAVIS LEONORA , COSAND WESLEY L.
Published: August 2010

During the solid‐phase synthesis of over 100 peptides, we have observed that the ethylcarbamoyl group is useful for the side chain protection of cysteine in peptides containing a single cysteine residue. The ethylcarbamoyl group is stable to the conditions of acidolytic cleavage, purification and long term storage. Brief treatment of peptides containing an S‐ethylcarbamoylcysteine residue with aqueous sodium hydroxide gives the deprotected cysteine peptide that can be coupled to carrier molecules such as proteins to give immunogen conjugates.
Use of tetrabutylammonium salts of amino acids in peptide synthesis
Authors: ANDREEVA L.A. , ALFEEVA L.Y. , POTAMAN V.N. , NEZAVIBATKO V.N.
Published: August 2010

Tetrabutylammonium (TBA) salts of amino acids and peptides have increased solubility, as compared with that of alkali metals salts, in organic solvents. We have compared the reaction rates for tripeptide formation in methylene chloride from Boc‐Gly‐Phe activated with various phenols, N‐oxysuccinimide and azide, and TBA‐salt of tryptophan, as well as Trp‐OCH3. H‐Trp‐O− TBA+ as an amino component significantly accelerates the rate of reaction. Although a significant degree of racemization has been found, the use of TBA‐salt of amino acids and peptides is justified in many cases due to high conversion rates.
Solid phase synthesis of peptides containing the non‐hydrolysable analog of (O)phosphotyrosine, P(CH2PO3H2)Phe
Authors: GARBAY‐JAUREGUIBERRY C. , FICHEUX D. , ROQUES B.P.
Published: August 2010

Studies about phosphorylation‐dephosphorylation mechanisms require the development of probes capable of being used in in vitro and in vivo conditions. We show in this work that the chemically and enzymatically stable p(CH2PO3H2) Phe analog of (O)phosphotyrosine can be easily introduced in peptides by the solid‐phase method. It has been incorporated in the 344‐357 sequence of the β2 adrenergic receptor in place of the Tyr residue in position 350 and/or 354 in order to investigate the role of tyrosine phosphorylation in the receptor agonist‐induced down‐regulation. Since p(CH2PO3H2)Phe is an ionized hydrophilic residue, peptides containing this amino acid do not easily permeate the cellular membranes. Therefore the modified amino acid was introduced in the synthetic pathway in its N‐Boc‐p(CH2PO3Et2)Phe form, which could be partially or completely deprotected. Coupling steps, including that of the new amino acid, were performed with good yields (~60% total yield) and further deprotections provided both the p(CH2PO3H2)Phe and p(CH2PO3HEt)Phe containing peptides with yields of around 20% each. The structure of the peptides was assessed by NMR, mass spectroscopy and amino acid analysis and the new amino acid was characterized under its phenyl‐thiocarbamyl form (PTC).