bluuebunny/crossref_metadata_2025 huggingface dataset:
REDUCTION AND REOXIDATION OF BOVINE PROINSULIN. EFFECT OF pH, ZINC IONS, TEMPERATURE AND CONCENTRATION
Authors: Markussen Jan , Heding Lise G.
Published: August 2010

The influence of pH, temperature and the concentrations of zinc ions and reduced proinsulin upon the yields of reoxidized proinsulin were studied using the insulin radioimmunoassay. The optimal conditions were found to be pH 8.5, absence of zinc ions and a low protein concentration. However, even at a concentration of reduced proinsulin of 1.47 μM, the reoxidized proinsulin did not compete with 125I‐insulin for the insulin antibodies as strongly as did genuine proinsulin. At high concentrations of reduced proinsulin (14.7 μM), the yield increased with decreasing temperature; at a 10‐times lower concentration the temperature had no influence upon the yields. Adsorption of reduced prosinulin to glassware was either irreversible or had a denaturing effect rendering the products immunologically inactive. Spontaneous reoxidation of reduced proinsulin is a rather delicate process, and the optimal conditions are different from those present in vivo.

When the reduction of proinsulin was carried out at a concentration of 31.5 μM, zinc ions were found to stabilize the reduced protein against denaturation and precipitation for more than 24 hours. However, at this concentration, reduced proinsulin is in a thermodynamic ally unstable state, both with and without zinc.
HYDROLYSIS OF AMINO‐ACID ESTERS BY ALKALINE MESENTERICOPEPTIDASE
Authors: Genov Nicolay , Shopova Maria
Published: August 2010

The Vmax and Km values for the hydrolysis of Nα‐tosyl‐L‐arginine methyl ester, Nα‐benzoyl‐L‐arginine methyl ester, N‐acetyl‐L‐tryosine ethyl ester and N‐benzoyl‐L‐tyrosine ethyl ester by alkaline mesentericopeptidase were determined. It is concluded that there is a similarity in the esterolytic properties of mesentericopeptidase and the subtilisins. Mesentericopeptidase is nearer to subtilisins Novo and Amylosacchariticus than to subtilisin Carlsberg. The Km values for the hydrolysis of Na‐tosyl‐L‐arginine methyl ester by alkaline mesentericopeptidase were approximately constant over the pH range 5.5 to 8.0. A pK of 6.6 at 37° C was determined from the sigmoid pH‐velocity profile for the hydrolysis of this substrate. The data indicate that there is an imidazole group in the active site of the alkaline protease from Bac. mesentericus that must be non‐protonated for hydrolysis to take place. The amino acid compositions of mesentericopeptidase and subtilisin Amylosacchariticus are almost identical, but there are differences in the mechanism of action of these two enzymes. The conclusion is drawn that alkaline mesentericopeptidase belongs to the subtilisin BPN'‐group of alkaline proteases according to the classification of Keay & Moser (14).
SYNTHESES OF FURTHER ANALOGUES OF NORPHALLOIN. GLY1‐, L‐VAL1‐ AND D‐ABU2‐ NORPHALLOIN AND (β‐TRIDEUTERO)‐ALA5‐ NORPHALLOIN*
Authors: Heber Helmut , Faulstich Heinz , Wieland Theodor
Published: August 2010

The norphalloin analogues with glycine and L‐valine instead of L‐alanine in position 1, (II and III), with D‐α‐aminobutyric acid instead of D‐threonine in position 2 (IV), and with β‐trideutero‐L‐alanine instead of L‐alanine in position 5 (β‐D3‐I), have been synthesized according to Chart I, mainly using the mixed anhydride method. For the final cyclization step to III the p‐nitrophenylester method was employed. Analogue IV showed toxicity in the white mouse with doses <5 mg per kg body weight, whereas II and III were nontoxic. The deuterated norphalloin analogue proved by p.m.r. measurement that in fact the methyl group of alanyl residue no.5 is located above the indole nucleus, as suggested in a former publication (4).
A SYNTHETIC STUDY OF THE EFFECT OF TYROSINE AT POSITION 120 OF RIBONUCLEASE
Authors: Hodges R. S. , Merrifield R. B.
Published: August 2010

[Tyr120]‐RNase 111–124 and [Ala120]‐RNase 111–124 were synthesized and purified to chromatographic and electrophoretic homogeneity. The peptides were mixed noncovalently with RNase 1–118 that had been prepared by enzymatic degradation of native bovine pancreatic ribonuclease A. The activities of the resulting complexes were compared with that of the corresponding complex containing the natural peptide sequence, [Phe120]‐RNase 111–124, and with native RNase, using yeast RNA, C > p and U > p as substrates. The Tyr120 and Phe120 complexes were equally active against RNA and C > p, but the Tyr120 complex was twice as active as the Phe120 complex against U > p. The complex with alanine at position 120 was only 1% as active toward C > p as the complex containing phenylalanine. The prediction that giraffe RNase, which contains tyrosine at position 120, would be relatively more active toward U > p than C > p compared with bovine RNase was verified.
A POTENTIOMETRIC AND CD STUDY ON THE β‐RANDOM COIL TRANSITION OF POLY‐L‐TYROSINE IN AQUEOUS SOLUTION
Authors: Cosani A. , Palumbo M. , Terbojevich M. , Peggion E.
Published: August 2010

The pH induced coil‐β transition of poly‐L‐tyrosine has been investigated by potentiometric and CD techniques. The “poly‐electrolyte” plot pKα vs. a shows the characteristic behaviour of polypeptides undergoing a conformational transition. CD measurements carried out on samples of the polymer solution under titration indicated that the polymer conformation changes within the same range of degrees of ionization as the titration curve exhibits the characteristic “hump”. Taking into account literature data on the aggregation process during the titration, the conclusion was made that β‐structure formation parallels aggregation.

The stability of the β‐structure of (L‐Tyr)r was found to decrease by increasing the temperature to 60°C. These results are discussed in terms of the solvation effects of the polymer side‐chains.
THE ENNIATIN IONOPHORES. CONFORMATION AND ION BINDING PROPERTIES
Authors: Ovchinnikov Yu. A. , Ivanov V. T. , Evstratov A. V. , Mikhaleva I. I. , Bystrov V. F. , Portnova S. L. , Balashova T. A. , Meshcheryakova E. N. , Tulchinsky V. M.
Published: August 2010

The ability of enniatins to bind alkali metal, alkaline earth metal and certain transition metal ions in solution has been investigated. The complexes have been shown to form in 1:1, 2:1 and 3:2 macrocycle:cation ratios; their stability constants have been determined, and the conditions favoring their formation have been established. The enniatins were shown to be complexones of very wide spectrum, displaying low metal ion selectivity in alcoholic solutions.

Two basic spatial forms, the non‐symmetric N3 form (in nonpolar solvents) and the symmetric P form (in polar solvents) have been disclosed and proposals made as to their conformational parameters. The molecular structure of the enniatin complexes has been established. Independent of the complexed ion species, of the complex stoichiometry, or of the type of solvent, the enniatin backbone of the complex is in the P form. In the 1:1 complexes, the ion is accommodated in the molecular cavity, forming iondipole bonds with all the amide and ester carbonyls. The depsipeptide chain of the enniatins is flexible, permitting “adaptation” of the complexone to the size of the ion, and thus explaining the low selectivity of these complexones. In the 2:1 and 3:2 complexes the cation is sandwiched in between two molecules of the antibiotic at the symmetry axis and interacts mainly with the N‐methylamide carbonyls. In these “sandwich” complexes the cation is much better screened from the anion and solvent than in the equimolar complexes and is highly soluble in organic solvents.

The data presented here may serve as basis for interpreting the dependence between the structure, metal complexing behavior and membrane‐affecting properties in the series of the naturally occurring enniatin ionophores and their synthetic analogs.
THERMOPHILIC AMINOPEPTIDASE FROM BACILLUS STEAROTHERMOPHILUS.
Authors: Balerna M. , Zuber H.
Published: August 2010

1. In mesophilic cells (37°C culture) of B. stearothermophilus a high molecular weight aminopeptidase (APIm) was found in the “membrane” fraction after lysozyme treatment and ultrasonication. APIm, which is also present in 55°C cells but in a 30‐fold lower amount, could be extracted from the “membranes” by carbonate‐bicarbonate buffer pH 9.6 and was further purified. APIm has a mol. wt. of about 400,000 and has an oligomeric structure (mol. wt. of subunits 46,000 ± 3,000). The “membrane‐bound” and the soluble enzyme differ in thermostability: The former bound‐enzyme is more thermostable. Specificity: Dipeptides are poor and tri‐ and tetrapeptides are good substrates with Gly, Leu, Ala or Met at the N‐terminus. In tripeptides the enzyme splits preferentially the first (N‐terminal) peptide bond.

2. Aminopeptidase III (APIII), which is synthesized in 37°C cultures of B. stearothermophilus in a 10‐fold higher amount than in 55°C cultures, was purified to homogeneity by a four‐step purification procedure. Mol. wt. of APIII: 108,000 and of the subunits 47,500 ± 3,000 (dimer). APIII is not thermostable at 60–70°C. The amino acid composition of APIII for some amino acids (Lys, His, Thr, Pro, Ala, Met, Ile, Tyr, Phe) is very similar to the composition of APII, and for Lys, His, Arg, Thr, Glu, Pro, Phe it is similar to that for thermophilic API. The most striking feature of this enzyme is its specificity as aminotripeptidase.
STUDIES ON A PROTAMINE (GALLINE) FROM FOWL SPERM.
Authors: Nakano Minoru , Tobita Tohru , Ando Toshio
Published: August 2010

Galline, a protamine from rooster sperm nuclei, has already been separated into its components, G‐I‐G‐VIII. The amino acid composition of the homogeneously purified fraction G‐I is determined decisively to be Arg11, Ser2, Gly3, Val1 and Tyr2, and the molecular weight is 2,908 as hydrochloride. The complete amino acid sequence was deduced as follows from the results of analyses of the tryptic and chymotryptic peptides: H‐Ser‐Gly‐Gly‐Val‐Arg‐Arg‐Arg‐Arg‐Tyr‐Gly‐Ser‐Arg‐Arg‐Arg‐Arg‐Arg‐Arg‐Arg‐Tyr‐OH.

Another purified fraction, G‐V, has the amino acid composition, Arg24, Thr1, Ser8, Gly3, Ala2, Pro2 and Tyr2 as described previously, and the molecular weight 6,274 as hydrochloride. The complete amino acid sequence was established by combining analytical results of tryptic, chymotryptic and thermolysin peptides as well as those of carboxypeptidase and leucine aminopeptidase digestion as follows: H‐Ala‐Arg‐Tyr‐Arg‐Ser‐Gly‐Arg‐Ser‐Arg‐Ser‐Arg‐Arg‐Thr‐Arg‐Arg‐Arg‐Arg‐Ser‐Pro‐Arg‐Ser‐Arg‐Gly‐Arg‐Ser‐Pro‐Arg‐Arg‐Arg‐Arg‐Ser‐Arg‐Arg‐Arg‐Arg‐Arg‐Tyr‐Gly‐Ser‐Ala‐Arg‐Arg‐OH.
BOVINE SERUM ALBUMIN IN LITHIUM CHLORIDE SOLUTIONS. III. A Comparative Study of Li+ and H3O+ Effects
Authors: Sun S. F. , Chang T. S.
Published: August 2010

The effects of Li+ and H3O+ on the conformation of bovine serum albumin in aqueous solutions at room temperature are compared. At low pH (high concentration of H3O+) the change in conformation of the protein is demonstrated by an increase in effective volume, a decrease in helical content and a blue shift of tyrosyl residue. A similar change is observed for the protein in highly concentrated LiCl solution (6.0–7.0 M) at neutral pH. However, the H3O+ is 12,000 times more powerful than the Li+ in destabilizing the protein molecule. This is consistent with their thermodynamic and kinetic properties, since the H3O+ is often different from the Li+ in several orders of magnitude. While the changes in structural properties of the protein are almost identical in both the acidic solution and the highly concentrated LiCl solution, further study using dioxane as a probe suggests different mechanisms under which the changes occur. The effect of H3O+ is related to electrostatic force, whereas the effect of Li+ is related to both the electrostatic and hydrophobic forces. These two major forces are believed to be responsible for the conformation of protein molecules.
SENSITIVITY OF GELATIN AND ALBUMIN TO IRRADIATION AT 230 NM*
Authors: Friedberg Felix , Nandedkar Arvind K. N.
Published: August 2010

Gelatin or poly‐L‐tyrosyl gelatin shows extensive degradation when exposed to ultraviolet radiation at a wavelength of 230 nm. Bovine serum albumin, a globular protein, exposed either to such ultraviolet radiation or to γ‐irradiation in the solid state resists the photolysis of peptide bonds. Molecular weights are determined by the ultracentrifugal “low speed” sedimentation equilibrium method. The effect of different speeds on the apparent average molecular weight of heterogeneous material is clearly illustrated.
SYNTHESIS OF THE PENTADECAPEPTIDE SEQUENCE OF THE ACTIVE SITE OF RABBIT MUSCLE TRIOSEPHOSPHATE ISOMERASE
Authors: Channabasavaiah K. , Sivanandaiah K. M.
Published: August 2010

The pentadecapeptide fragment, Trp‐Val‐Leu‐Ala‐Tyr‐Glu‐Pro‐Val‐Trp‐Ala‐Ile‐Gly‐Thr‐Gly‐Lys, which constitutes a part of the active site of rabbit muscle triosephosphate isomerase has been synthesized. It does not exhibit any catalytic activity typical of triosephosphate isomerase.
SYNTHESIS OF PEPTIDES BY FRAGMENT CONDENSATION ON A SOLID SUPPORT.
Authors: Ragnarsson Ulf , Karlsson Sune M. , Hamberg Ulla
Published: August 2010

Two tripeptides and one dipeptide, protected except at the carboxyl ends, have been prepared in solution and used as intermediates in a new synthesis of bradykinin on a solid support. Condensation of the two tripeptides to the resin was effected in satisfactory yield with dicyclohexylcarbodiimide plus N‐hydroxysuccinimide. The partial epimerization that might occur by such an approach was explicitly verified to be without practical importance in this case. The crude product contained only traces of impurities and yielded, after purification, bradykinin of high purity. Both the crude and purified bradykinin exhibited full biological activity.
BREATHING MODE OF CONFORMATIONAL FLUCTUATIONS IN GLOBULAR PROTEINS
Authors: Suezaki Yukio , Gö Nobuhiro
Published: August 2010

Globular proteins in the native state are assumed to behave as continuous elastic spheres in the low frequency breathing motions. Reasonable values of Young's modulus E = 1011dyne/cm2and the radius of the sphere r0 = 20 Å, yield a wave number of 26 cm‐1for the fundamental vibration of the sphere. The peak at around 30 cm‐1in the laser Raman spectra of native α‐chymotrypsin and pepsin observed by Brown et al. might be assigned to the breathing motion which the native proteins undergo as continuous elastic bodies.
NMR INVESTIGATIONS OF PROLINE AND ITS DERIVATIVES.
Authors: Pogliani L. , Ellenberger M. , Valat J. , Bellocq A.M.
Published: August 2010

The proton magnetic resonance (PMR) spectrum of acetyl‐proline amide in D2O solution has been analysed by computer simulation. The spectra of the cis and the trans isomers have been separated and their PMR parameters (chemical shift and coupling constants) are given. Vicinal coupling constants of the pyrrolidine ring are interpreted by means of a Karplus zone relation. The chemical shift effect of the anisotropy of both peptide planes is considered. It follows that both isomers are puckered with Cγin an endo position, but the cis isomer is more rigid than the trans isomer, which moreover undergoes a small interconversion of the Cγand Cδatoms between two extreme spatial positions. The dihedral angle SP has different values in both isomers. Thus, the dihedral angle between the two peptide planes is smaller in the trans isomer than in the cis isomer.
FREQUENCY‐DEPENDENT DIFFRACTION FROM ENZYMATIC BREATHING MODES
Authors: Morgan R. S. , Peticolas W. L.
Published: August 2010

The intensity of the time‐dependent Fourier transform of any macro‐molecule which contains a cleft of the sort that exists in the protein lysozyme is derived. It is shown that there is a region of this transform in which this intensity varies nearly sinusoidally with time with a frequency equal to that of the macromolecule's breathing mode of vibration, and where, therefore, the diffracted power will be primarily at this single frequency. Observation of this power will allow the experimental determination of the frequency of this mode, which is expected to be much lower than those observable by Raman spectroscopy.
STUDIES ON THE CONFORMATION AND INTERACTIONS OF ELASTIN: NUCLEAR MAGNETIC RESONANCE OF THE POLYHEXAPEPTIDE
Authors: Urry D. W. , Ohnishi T. , Long M. M. , Mitchell L. W.
Published: August 2010

Synthesis, proton magnetic resonance and carbon‐13 magnetic resonance characterizations, including complete assignments, are reported for the polyhexapeptide of elastin, HCO‐Val‐(Ala1‐Pro2‐Gly3‐Val4‐Gly5‐Val6)18‐OMe. Temperature dependence of peptide NH chemical shifts and solvent dependence of peptide C‐O chemical shifts have been determined in several solvents and have been interpreted in terms of four hydrogen bonded rings for each repeat of the polyhexapeptide. The more stable hydrogen bonded ring is a β‐turn involving Ala1 C‐O…HN·Val4 More dynamic hydrogen bonds are an 11‐atom hydrogen bonded ring Gly3 NH · O‐C Gly5, a 7‐atom hydrogen bonded ring (a γ‐turn) Gly3 C‐O … HN · Gly5 and a 23‐atom hydrogen bonded ring Val61NH … O‐C Val6(l+l).

This set of hydrogen bonds results in a right‐handed β‐spiral structure with slightly more than two repeats (approximately 2.2) per turn of spiral. The β‐spiral structure is briefly discussed relative to data on the elastic fiber.
CONFORMATIONAL STUDIES ON SEQUENTIAL POLYPEPTIDES. PART VI. STRUCTURAL INVESTIGATIONS ON (Pro‐Leu‐Gly)10, (Pro‐Leu‐Gly)n AND (Leu‐Pro‐Gly)n
Authors: Scatturin A. , Tamburro A. M. , del Pra A. , Bordignon E.
Published: August 2010

The conformational properties of (Pro‐Leu‐Gly)10, (Pro‐Leu‐Gly)n and (Leu‐Pro‐Gly)n were investigated both in solution and in solid state. By circular dichroism studies it was possible to demonstrate the formation of an ordered collagen‐like structure for (Pro‐Leu‐Gly)n in hexafluoroisopropanol–water mixtures and in ethylene glycol; (Leu‐Pro‐Gly)n assumes an ordered conformation only in ethylene glycol; (Pro‐Leu‐Gly)10 is unordered under all the conditions studied.

X‐ray diffraction patterns indicated that (Pro‐Leu‐Gly)n and (Leu‐Pro‐Gly)n assume a triple helical structure in solid state. In addition, the investigation of (Pro‐Leu‐Gly)n strongly suggests that this type of structure is a single chain triple helix. The X‐ray patterns of (Pro‐Leu‐Gly)10 do not allow us to ascertain a collagen or polyproline II‐like structure for this decatripeptide.
REACTIONS OF PROTEINS WITH ETHYL VINYL SULFONE*
Authors: Friedman Mendel , Finley John W.
Published: August 2010

Ethly vinyl sulfone (EVS) alkylates ε‐amino groups of lysine side chains and imidazole groups of histidine residues in proteins. Amino acid analysis of hydrolyzates of EVS‐treated polylysine shows that lysine forms two derivatives, presumably ε‐N‐(ethylsulfonylethyl)lysine and ε, N, N‐bis(ethylsulfonylethyl)lysine that are eluted as well‐resolved peaks on the (long basic) physiological column of our amino acid analyzer at about 118 and 60 min, respectively. Peaks with identical elution times were also observed after EVS‐treatment of BSA and wool. The postulated histidine derivative, presumably N3‐im‐(ethylsulfonylethyl)histidine is also eluted as a well‐resolved peak on the same column at about 90 min. A peak with an identical elution time was observed in a hydrolyzate of EVS‐treated polyhistidine. The described alkylation has potential utility for modifying proteins.
THE SYNTHESIS AND BIOLOGICAL ACTIVITY OF [165, 182, 189‐S‐CARBAMIDOMETHYLCYSTEINE]‐HUMAN GROWTH HORMONE‐(140–191)*
Authors: Blake James , Li Choh Hao
Published: August 2010

The peptide [165, 182, 189‐S‐carbamidomethylcysteine]‐human growth hormone‐(140–191) has been synthesized by the solid‐phase method. The complement fixation, lactogenic and growth‐promoting activities of the synthetic peptide were comparable to that of [165, 182, 189‐S‐carbamidomethylcysteine]‐human growth hormone‐(141–191) that was derived from the native hormone.
ON THE CONFORMATION OF THE DISULPHIDE GROUP IN L‐CYSTINE AND ITS DERIVATIVES*
Authors: Pattabha Vasantha , Srinivasan R.
Published: August 2010

The terminal groups in cystine are asymmetric and hence the disulphide group with right and left chirality may not have equal energy. An attempt is made to resolve this problem through energy calculation using semi‐empirical methods involving non‐bonded and electrostatic interactions and simple Pauling type torsional potential for the disulphide group. The results are discussed in the light of experimental data.
NON‐RANDOM RELATIONSHIPS AMONG AMINO ACIDS IN PROTEIN SEQUENCES
Authors: Black John A. , Harkins Richard N. , Stenzel Peter
Published: August 2010

We have computed the observed distribution of amino acid pairs n, n + 1 up to n, n + 10 within 100 unrelated protein sequences containing a total of 14,034 amino acids. The expected distribution of the same amino acid pairs was calculated assuming that the amino acids within each sequence are arranged in random order. Statistical analysis of the data shows that amino acids in the n, n + 1 and n, n + 3 relationship deviate from random expectation at the 1% level of significance. These relationships are consistent with known secondary structures; however, there are no amino acid pairs which obviously contribute to the non‐random result.
CHARACTERIZATION OF AN ALKALINE SUBTILOPEPTIDASE TYPE PFIZER
Authors: Munnelly K. P. , Kapoor A.
Published: August 2010

The physicochemical properties, amino acid composition and profile of the tryptic peptides for an alkaline subtilopeptidase type Pfizer have been determined. The enzyme is stable in the pH range from 5 to 10, has a pH optimum of 9.5 to 10, and is relatively stable for a period of 2 h up to a temperature of 50°C. Homogeneity was demonstrated by electrophoretic techniques and the mobilities indicated an isoelectric point of 8.7. The molecular weight was found to be 25,000 by gel filtration. The amino acid composition was found to be Ala32, Arg4, Asp78, Glu15, Gly29, His4, Ile9, Leu13, Lys11, Met5, Phe4, Pro14, Ser31, Thr17, Tyr9, Val22, a total of 247 amino acid residues. The enzyme does not contain either disulfide bonds or cysteine, and lacks tryptophan as well. The N‐terminal end‐group residue is alanine: the C‐terminal amino acid is arginine. Tryptic hydrolysis of the enzyme produced 15 peptides which were separated by gradient elution on Dowex 50‐X2. The amino acid composition of each appropriately purified tryptic peptide was established.
SOLID PHASE SYNTHESIS AND SOME PHARMACOLOGICAL PROPERTIES OF 8‐D‐HOMOARGININE‐VASOPRESSIN AND 1‐DEAMINO‐8‐D‐HOMOARGININE‐VASOPRESSIN
Authors: Lindeberg E. Gunnar G. , Melin Per , Larsson Lars‐Eric
Published: August 2010

Fully protected 8‐D‐lysine‐vasopressin and 1‐deamino‐8‐D‐lysine‐vasopressin were synthesized by the solid phase method. Selective removal of the lysine protection and reaction with 1‐guanyl‐3,5‐dimethylpyrazole converted D‐lysine into D‐homoarginine. The title compounds were then obtained by treatment with sodium in liquid ammonia and oxidation in dilute aqueous solution. Although the antidiuretic activities are lower than for the corresponding D‐arginine derivatives, the even lower pressor effects make the new analogues highly specific antidiuretic agents. The A/P ratios for 8‐D‐homo‐arginine‐vasopressin and its 1‐deamino derivative are 100 and 3,300, respectively.
FIBRINOPEPTIDES. IV.
Authors: Channabasavaiah K. , Sivanandaiah K. M.
Published: August 2010

Human fibrinopeptide A, a hexadecapeptide, released by the action of thrombin on fibrinogen during clotting of blood, has been synthesized by conventional methods. The synthetic peptide as well as some of the intermediates in the synthesis have been examined for anticoagulant activity. Though all of them were found to be active, the terminal carboxyl protected peptides are more potent inhibitors of clotting than the carboxyl free peptides.
INACTIVATION OF TRYPSIN AND CHYMOTRYPSIN WITH A PHOTOSENSITIVE PROBE
Authors: Tometsko Andrew M. , Turula Jon
Published: August 2010

The photosensitive inactivation of trypsin and chymotrypsin by 4‐fluoro‐3‐nitrophenyl azide (FNPA) is described. A dark inhibition was observed at elevated probe concentrations, and was reversible. The enzymes were stable to photolysis in the absence of probe. Photolytic inactivation of trypsin and chymotrypsin with FNPA was found to be irreversible, and occurs in minutes at concentrations of FNPA where dark inhibition is negligible. The photoprobe was equally effective at pH 3 or pH 8. Nonspecific inactivation appears to be low, as evidenced by the stability of glucose oxidase and peroxidase to photolysis with FNPA.
CHEMICAL STUDY OF THE TOPOGRAPHY OF PORCINE LUTROPIN (LH)* USING DINITROFLUOROBENZENE AND DANSYL CHLORIDE
Authors: Combarnous Yves , Hennen Georges
Published: August 2010

Treatment of porcine lutropin β‐subunit by increasing amounts of dansyl chloride shows that only one fluorescent group can be bound to the free subunit, namely on tyrosine β‐37. This modification prevents reassociation with native α‐subunit.

In contrast to dansyl chloride, dinitrofluorobenzene reacts preferentially with tyrosine β‐59. This substitution does not interfere with the reassociation with the native α‐subunit.

By using equimolar ratio of dansyl chloride and porcine lutropin α‐subunit it is possible to modify this subunit on a single site, which is found to be a tyrosine residue. The monodansylated α‐subunit is still able to recombine with native β‐subunit but its fluorescence is found to be markedly quenched upon binding. In addition, the O‐dansyltyrosyl fluorescence quenching by potassium iodide is more effective on the recombined dimer than on the free α‐subunit.

Both reconstituted dimers (native α x dinitrophenylated β and dansylated α x native β) are without biological activity. It is not clear whether the substituted phenolic groups are essential or whether the added groups prevent the αβ dimer from taking the active conformation. This alternative is discussed in the light of recent data from this laboratory and others.
SYNTHESIS OF PEPTIDES AND DERIVATIVES OF 3‐ AND 4‐ HYDROXYPROLINE
Authors: Adams Elijah
Published: August 2010

Synthesis and properties are reported for a number of peptides and related derivatives of 3‐hydroxy‐L‐proline and 4‐hydroxy‐L‐proline. These were made for several different purposes, namely, synthesis of N‐acetyl‐O‐tosyl‐4‐hydroxy‐L‐proline amide as a model for chemical reduction of peptide‐bound hydroxyproline, synthesis of tripeptides with the sequence glycyl‐4‐hydroxy‐L‐prolyl‐X, synthesis of the naturally occurring sequence, glycyl‐3‐hydroxy‐L‐prolyl‐4‐hydroxy‐L‐proline, and monomers for polymerization to yield the sequence ‐glycyl‐prolyl‐4‐hydroxy‐L‐prolyl‐.
ISOLATION AND CHARACTERIZATION OF A NEW TRYPSIN‐LIKE ENZYME FROM: Tenebrio molitor L. LARVAE
Authors: Levinsky Haim , Birk Yehudith , Applebaum Shalom W.
Published: August 2010

A trypsin‐like enzyme (TLE) was separated and purified from Tenebrio molitor larval midgut enzyme solution by ion‐exchange chromatography on a DEAE‐cellulose column. The purified enzyme was found to be a homogeneous protein by electrophoresis in polyacrylamide gels and on cellulose acetate strips, by electrofocusing in polyacrylamide gels and by SDS‐polyacrylamide gel electrophoresis. Its molecular weight was estimated to be 18300 by ultracentrifugal analysis and 24300 on SDS‐polyacrylamide gel electrophoresis. It has an isoelectric point 8.0, it contains only four half‐cystine residues per molecule and the NH2‐terminal amino acid is isoleucine. TLE possesses a high degree of specificity towards trypsin synthetic substrates such as N‐α‐benzoyl‐DL‐arginine p‐nitroanilide (BAPNA), p‐tosyl‐L‐arginine methyl ester (TAME) and poly‐L‐lysine hydrobromide. The optimal pH for TLE activity was found to be 8.0 and the optimal temperature 50° C. Its Km value when assayed on BAPNA was 0.93mM and on TAME 0.08mM. TLE is stable at neutral pHs and its activity is not affected by Ca2+ and by 0.01 M 1, 4‐dithiothreitol (DTT). It is inactivated by DFP and tosyl‐L‐lysine chloromethylketone (TLCK) and is fully inhibited by the naturally occurring trypsin inhibitors such as trypsin‐and α‐chymotrypsin inhibitor (AA) from soybeans, basic pancreatic trypsin inhibitor (BPTI), chick peas trypsin and chymotrypsin inhibitor (CI) and crystalline soybean trypsin inhibitor (CSBTI), forming with them complexes in a molar ratio of 1:1. The Ki value for AA with BAPNA as substrate is 5.87 10‐7 M and for BPTI 7.92 10‐7M.

No common antigenic determinants were noted between TLE and bovine trypsin. This finding together with the relatively low number of ‐S‐S‐ bonds in the TLE molecule indicate that TLE differs in conformation from bovine trypsin.
STUDIES ON GROUNDNUT PROTEINS. VI. ISOLATION, CHARACTERISATION AND HYDROGEN ION TITRATION OF CONARACHIN II
Authors: Shetty K. Jayarama , Rao M. S. Narasinga
Published: August 2010

A method is described for isolating conarachin II in a homogeneous form by the techniques of DEAE‐cellulose chromatography, polyacrylamide gel electrophoresis and sedimentation velocity. The protein contains 0.72% carbohydrate and no phosphate. Hydrogen ion titration curve indicated that the sidechain carboxyl, imidazole and ‐amino groups titrated with normal pK Int values and their number agreed with the analytical values obtained from amino acid analysis. However, tyrosine phenolic groups had abnormal pK Int of 10.5.
AFFINITY CHROMATOGRAPHY OF SEVERAL PROTEOLYTIC ENZYMES ON CARBOBENZOXY‐D‐PHENYLALANYL‐TRIETHYLENETETRAMINE‐SEPHAROSE*
Authors: Fujiwara Kunio , Tsuru Daisuke
Published: August 2010

Carbobenzoxy‐D‐phenylalanyl‐triethylenetetramine‐Sepharose (Z‐D‐Phe‐T‐Sepharose) was found to be an effective affinity adsorbent for several proteolytic enzymes which preferentially catalyze the hydrolytic cleavage of peptide bonds involving amino or carboxyl groups of hydrophobic and bulky amino acid residues. α‐Chymotrypsin, subtilisin and neutral metalloendopeptidase were adsorbed at pH 5–7, while pepsin and Rhizopus niveus acid protease showed affinity to the adsorbent at pH 3.5–5.0. α‐Chymotrypsin was recovered by elution with 0.1 M acetic acid and neutral subtilopeptidase (B. subtilis neutral protease) was eluted with 0.5 M NaCl at pH 9.0. Subtilisin and thermolysin were found in the eluates with 1.5 M guanidine‐HCl, 1 M p‐toluenesulfonate or 30% ethylene glycol at pH 7. Rhizopus acid protease was eluted with 0.5 M acetic acid and pepsin with 1 M guanidine‐HCl or p‐toluenesulfonate at pH 3.5. The chromatographic purifications by this method of highly purified or crystallized enzyme preparations commercially available resulted in 1.3–1.5‐fold increase in their specific activities. Inactivation of these proteolytic enzymes by chemical modification, and formation of enzyme‐inhibitor complex led to loss of the binding ability to the adsorbent. On the other hand, the zinc‐free apoenzymes of neutral subtilopeptidase and thermolysin were adsorbed onto and eluted from the adsorbent column under the same conditions as those for the native enzymes, suggesting that zinc is not essential for the binding of the substrate to these metalloproteases.
SYNTHESIS AND BIOLOGICAL ACTIVITY OF POSITION 1 ANALOGS OF LH‐RH
Authors: NikolicS Karoly , Coy David H. , Vilchez‐Martinez Jesus A. , Coy Esther J. , Schally Andrew V.
Published: August 2010

(Formyl‐sarcosine)1‐LH‐RH (I), (acetyl‐sarcosine)1‐LH‐RH (II), (2‐pyrrolidone‐4‐carboxylic acid)1‐LH‐RH (III), (N‐methyl‐2‐pyrrolidone‐4‐carboxylic acid)1‐LH‐RH (IV, hydroxyproline1‐LH‐RH (V) and (cyclopentane‐carboxylic acid)1‐LH‐RH (VI) were synthesized by solid phase methods on a benzhydrylamine resin support. Peptides I‐IV were assayed for LH‐ and FSH‐releasing activity over a 4‐h period after subcutaneous injection into immature male rats in order to detect any prolongation of activity. The peptides were found to have the following integrated LH‐releasing activities compared with LH‐RH: I, 64%; II, 72%; III, 19%; IV, 58%. None of the peptides were found to be longer acting than LH‐RH. Peptides V and VI were far less active, 0.001% and 1.4%, respectively.
S‐CARBOXYMETHYLCYSTEINE SULFONE: INSTABILITY TO ACID HYDROLYSIS AND UNREACTIVITY WITH N‐TERMINAL REAGENTS
Authors: Zervos Constantine , Adams Elijah
Published: August 2010

An examination of the properties and reactivity of S‐carboxymethylcysteine sulfone indicated that, unlike S‐carboxymethylcysteine, the sulfone is not stable under acid hydrolysis conditions and decomposes to yield alanine. Unlike S‐carboxymethylcysteine, the sulfone is resistant to N‐derivatization by the dansyl reagent or by phenylisothiocyanate. Efforts were made to determine if spontaneous cyclization of the sulfone to the corresponding thiazane (lactam) accounts for lack of reactivity. These included i.r. spectroscopy, natural abundance 13C‐n.m.r. spectroscopy and differential scanning calorimetry, but yielded equivocal results concerning the existence of the cyclic form in solution. Solubility behavior of the sulfone after lyophilization from strongly acid solutions was consistent with conversion of the open chain form to the cyclic form on addition of water.
COMPARISON OF PROTEINS FROM THERMOPHILIC AND NONTHERMOPHILIC SOURCES IN TERMS OF STRUCTURAL PARAMETERS INFERRED FROM AMINO ACID COMPOSITION*
Authors: Singleton Rivers , Middaugh Charles R. , Macelroy Robert D.
Published: August 2010

The amino acid composition of 14 different proteins from thermophilic bacteria were compiled along with the amino acid compositions of 56 corresponding proteins from nonthermophilic sources. A comparison was made between proteins serving the same catalytic function, and significant differences in composition were noted for those proteins from thermophilic bacteria. However, no consistent pattern was evident and the differences were often small. The two data pools were treated as two distinct classes and a thermophilic versus nonthermophilic comparison of amino acid composition was made using the Student's t‐test. Significant differences in composition were found for Asx (sum of Asp and Asn, if known), Ser, and Arg. Both classes of data have similar standard deviations for the mean of any single amino acid, suggesting a similar tolerance of variation in the two classes of proteins. This would argue against the hypothesis that thermophiles exhibit a greater frequency of errors in protein synthesis. The amino acid compositions were used to calculate structural parameters (% helix, % beta, % turn, hydrophobicity, and melting temperatures) for the two classes of proteins. Of these, only the predicted % beta content was significantly lower for proteins of thermophilic origin. No differences in hydrophobicity or predicted melting temperature were observed for the two classes of proteins. This study supports the hypothesis that while small differences may occur in the amino acid composition of thermophilic proteins, they are quite varied and often are very subtle.
STUDIES ON CYTOCHROME C:
Authors: Borin Gianfranco , Filippi Bruno , Stivanello Diego , Marchiori Fernando
Published: August 2010

A solution synthesis of Z‐Gly‐Thr‐Lys (Tfa)‐Met‐Ile‐Phe‐Ala‐Gly‐Ile‐Lys (Tfa)‐Lys (Tfa)‐NHNH‐Boc corresponding to the sequence 77–87 of horse heart cytochrome c is described. The protected undecapeptide was obtained from intermediate hepta‐ and tetrapeptide fragments by an azide coupling.
THE EFFECTS OF DENATURANT AND TEMPERATURE ON THE CIRCULAR DICHROIC SPECTRUM OF OVINE LUTROPIN‐α
Authors: Puett David , Holladay Leslie A.
Published: August 2010

Circular dichroic (CD) spectra of the glycoprotein hormone subunit, lutropin‐α, have been obtained under denaturing conditions (6 M guanidinium chloride, GdmCl) with the disulfides intact, reduced, and reduced and S‐carboxymethylated. Above 260 nm, these spectra are similar (although not identical), showing that the disulfide chromophores do not contribute appreciably to the near ultraviolet CD spectrum under denaturing conditions. However, these spectra differ considerably from that of native lutropin‐α over this spectral region demonstrating that the tertiary structure of lutropin‐α has a major influence on the near ultraviolet CD spectrum. The magnitude of the 232.5 nm positive CD extremum of lutropin‐α was found to increase with increasing GdmCl concentration and with decreasing temperature. Between 5d̀C and 45d̀C, the ellipticity [θ] at 232.5 nm changed in a linear fashion with temperature; at other wavelengths the thermal changes in [θ] were quite small. [θ] at 232.5 nm increased by about 80% over a 3 M GdmCl range; in contrast, [θ] at 216 nm (indicative of β‐structure) exhibited maximal changes over a 0.5 M GdmCl range. These results indicate some conformational flexibility in lutropin‐α. The positive 232.5 nm CD extremum has been assigned to one or more tyrosyls which are influenced by an intact disulfide. The latter was demonstrated by showing that reduced and S‐carboxymethylated lutropin‐α failed to exhibit the positive extremum.
STUDIES ON POLYPEPTIDES:
Authors: Voskuyl‐Holtkamp Ingrid , Schattenkerk Cecile
Published: August 2010

A description is given of the synthesis by fragment condensation of the peptides Glu‐Ser‐Ser‐Ala‐Asp‐Lys‐Phe‐Lys‐Arg‐Gln‐His‐Met‐Asp and Gly‐Glu‐Ser‐Arg‐Glu‐Ser‐Ser‐Ala‐Asp‐Lys‐Phe‐Lys‐Arg‐Gln‐His‐Met‐Asp respectively corresponding to the 5–17 and 1–17 amino acid sequences of rat pancreatic ribonuclease.
β‐ENDORPHIN: SYNTHESIS AND MORPHINE‐LIKE ACTIVITY OF ANALOGS WITH D‐AMINO ACID RESIDUES IN POSITIONS 1, 2, 4 AND 5
Authors: Yamashiro Donald , Tseng Liang‐Fu , Doneen Byron A. , Loh Horace H. , Li Choh Hao
Published: August 2010

The solid‐phase syntheses of [D‐Tyr1]‐, [D‐Ala2]‐, [D‐Phe4]‐, and [D‐Met5]‐βc‐endorphins are described. A comparison of certain methods of purification and criteria of homogeneity is made with the use of these compounds. Bioassay of these synthetic analogs bothin vitroandin vivoshow that [D‐Ala2]‐βc‐endorphin possesses significant opiate activity whereas the other analogs have minimal activity.
A STUDY ON THE STABILITY OF DIPHENYLINDENONESULPHONYL DERIVATIVES OF AMINO ACIDS TO ACID HYDROLYSIS
Authors: Vladovska‐Yukhnovska Y. , IVANOV CH. P. , Yoakim M.
Published: August 2010

The stability of the diphenylindenonesulphonyl (disyl) derivatives of tryptophan, proline, hydroxyproline, histidine, serine, threonine and aspartic acid, as well as of glycine, alanine, α‐amino butyric acid, phenylalanine, valine, leucine and isoleucine to acid hydrolysis is studied. The results indicate that the disyl derivatives are much more stable in comparison with the corresponding DNP‐and DNS‐derivatives. Hence, the dysil‐chloride method possesses definite advantages over these widely used methods for determination of N‐terminal groups, not only because of its higher sensitivity, but also because of the higher stability of the disyl derivatives of amino acids to acid hydrolysis.
QUANTITATION OF THE β‐ELIMINATION REACTION AS USED ON GLYCOPROTEINS
Authors: Downs F. , Peterson C. , Murty V. L. N. , Pigman W.
Published: August 2010

The carbohydrate side chains of mucus‐type glycoproteins are O‐glycosidic bonds between N‐acetylgalactosamine to the hydroxyl groups of serine and threonine in the protein core. The alkaline catalyzed β‐elimination reaction, in the presence of sodium borohydride, is used for determining the number of side chains.

The present paper presents a study of the quantitativeness of the alkaline borohydride procedure, using four parameters: the loss of seryl and threonyl residues, the formation of alanine and 2‐aminobutanoic acid; the decrease in N‐acetylhexosamine and the recovery of the amino sugar alcohols. Bovine, ovine and porcine submandibular glycoproteins were studied.

Evidence is presented for the existence of N‐acetylglucosamine involvement in O‐glycosidic linkages to serine and threonine.

Results for the relative rates of β‐elimination indicate that serine‐linked glycosides are released more rapidly than threonine‐linked glycosides.
CYCLIC PEPTIDES
Authors: Shimohigashi Yasuyuki , Lee Sannamu , Aoyagi Haruhiko , Kato Tetsuo , Izumiya Nobuo
Published: August 2010

To confirm the structure of AM‐toxin I (a phytotoxic cyclotetradepsipeptide) the proposed peptide was prepared by a conventional method. The synthetic peptide and natural AM‐toxin I were identical as regards t.l.c., u.v., mass spectra and biological activity in causing necrosis on apple leaves. A prepared dimer of AM‐toxin I showed extremely weak activity; the relationship between the ring size and biological activity of AM‐toxin I is discussed.
QUENCHING OF TRYPTOPHAN FLUORESCENCE IN HUMAN ANTITHROMBIN III BY IODIDE ION
Authors: Einarsson Roland
Published: August 2010

Iodide is an efficient quencher of antithrombin III intrinsic tryptophan fluorescence. The quenching pattern indicates that about 60% of the tryptophyl fluorescence originates from exposed residues in the multitryptophan‐containing protein. In denaturing media all of the tryptophyls are solvent‐exposed. The binding of heparin to antithrombin III influences the number of solvent‐exposed tryptophan residues. By studying the dependence of the quenching on pH, information regarding the presence of charged residues adjacent to tryptophyls was obtained.
PHOTOCHEMICAL EVIDENCE FOR THE PRESENCE OF HISTIDYL RESIDUE IN THE ACTIVE SITE OF ALKALINE MESENTERICOPEPTIDASE
Authors: Shopova Maria , Genov Nicolay
Published: August 2010

The photosensitized oxidation of alkaline mesentericopeptidase in the presence of methylene blue results in a first‐order rate of inactivation. The loss of enzymatic activity towards casein and N‐acetyl‐L‐tyrosine ethyl ester closely correlates with the destruction of one histidyl residue. A pK value of 6.8 is determined from the sigmoid pH‐dependence of the photoinactivation rate. This suggests the involvement of a normal titrating imidazole group in the active site of mesentericopeptidase. The competitive inhibitor Nα‐benzoyl‐L‐arginine protects the enzyme from photoinactivation. A conclusion is made that the active site histidyl residue is modified.

Circular dichroism spectra show no change in the protein conformation during the photodynamic treatment.
REACTION OF BOVINE AND EQUINE GROWTH HORMONES WITH TETRANITROMETHANE
Authors: Daurat‐Larroque Silvia T. , Portuguez Manuel E. Moya , Santomé José A.
Published: August 2010

Bovine and equine growth hormones were chemically modified with tetranitromethane, at pH 7.4 during 5 h and at pH 8.0 in the presence of 8 M urea during 1 h.

a) Both hormones have very similar but not identical reactivities.

b) The nitration of the reactive tyrosines and tryptophan residues at pH 7.4 produces no detectable changes in their immunological or somatotrophic activities.

c) The nitration of all tyrosine residues in both hormones gives rise to a complete loss of somatographic activity with no alteration of the immunological activity.
STUDIES ON TRYPSIN INHIBITORS:
Authors: Tomatis Roberto , Guggi Augusto , Salvadori Severo , Rocchi Raniero
Published: August 2010

The synthesis, by fragment condensation, of protected peptides related to the N‐terminal (positions 1–14) and C‐terminal (positions 36–52) portions of the amino acid sequence of porcine pancreatic secretory trypsin inhibitor II (Kazal type) is described.

The α‐carboxyl function of the lysyl residue in position 14 was used as the free acid, or protected by the tert‐butyloxycarbonylhydrazide.

Two different synthetic pathways were used in the preparation of the 36–52 sequence of the inhibitor. The identity and purity of the synthesized peptide derivatives were established by amino acid analysis of acid hydrolysates, optical rotation and thin layer chromatography in two solvent systems. The final products were also evaluated, after partial deprotection with anhydrous hydrogen fluoride or aqueous 90% trifluoroacetic acid, by paper electrophoresis at different pH values and enzymic digestion with papain and aminopeptidase M followed by quantitative amino acid analysis.
PRELIMINARY X‐RAY CRYSTALLOGRAPHIC AND PHYSICO‐CHEMICAL INVESTIGATIONS OF HUMAN CERULOPLASMIN
Authors: Moshkov K. A. , Shavlovski M. M. , Zaitzev V. N. , Neifakh S. A.
Published: August 2010

Single crystals of the plasma protein ceruloplasmin (CP) and its two modified forms: neuraminidase‐treated CP (asialoCP) and NaN3‐inhibited CP (NaN3‐CP) suitable for X‐ray studies have been grown. The native CP crystallizes as described previously by Magdoff‐Fairchield et al. (1969) in the tetragonal space group 14 (a = b = 268.2 Å, c = 129.1 å) with two protein molecules in the asymmetric part of a unit cell. AsialoCP crystals belong to the trigonal space group P 3121 or P321 (a = b = 215.0 å, c = 84.5 å) and have one protein molecule in the asymmetric part of a unit cell. NaN3‐CP crystals are isomorphous to crystals of native CP. Despite some differences in electrophoretic mobility and optical properties, the conformations of the native CP molecule and its modified forms are similar, as can be concluded from a study of ORD and CD spectra.
SYNTHESIS AND BIOLOGICAL ACTIVITIES OF TWO ACTH‐ANALOGUES CONTAINING L‐NORARGININE IN POSITION 8
Authors: VAN Nispen J.W. , Tesser G.I. , Nivard R.J.F.
Published: August 2010

Two new ACTH‐analogues, an octadecapeptide amide and a tetracosapeptide containing the lower homologue of arginine (norarginine) in position 8, have been synthesized by the generally accepted method. Special attention was paid to the synthesis of the required tetrapeptide representing the 7–10 sequence, which was obtained either by direct introduction of L‐nitronorarginine or by amidination of the γ‐amino function in a protected peptide containing α, γ‐diaminobutyric acid.

Biological activity determination showed that the shortening of the arginine side chain in position 8 results in the formation of active ACTH‐analogues.
INVESTIGATION OF THE ROLE OF TRYPTOPHAN IN α‐MSH*:
Authors: VAN Nispen J. W. , Smeets P. J. H. , Poll E. H. A. , Tesser G. I.
Published: August 2010

Two analogues of α‐MSH are described, in which the tryptophan residue occuring in position 9 of the natural hormone has been replaced by pentamethyl‐phenylalanine and phenylalanine, respectively. The analogues were synthesized via a conventional procedure and the [Phe9]‐analogue also by a semi‐synthetic approach, which demonstrated thefavourable properties of the applied, new amino‐protecting Msc function for this purpose.

The widely different electron donor properties of the substituted residues were accompanied by a large difference in melanocyte stimulating activity of the analogues. The [Pmp9]‐analogue, having donor properties comparable to those of the natural compound, was four to five times more active than the analogue containing the poorly donating Phe residue. The opposite effect was noted in in vivo lipolysis in rabbits.
A COMPARISON OF THE AMINO‐TERMINAL SEQUENCES OF TWO CALF‐THYMUS CHROMATIN NON‐HISTONE PROTEINS
Authors: Walker J. M. , Goodwin G. H. , Johns E. W. , Wietzes P. , Gaastra W.
Published: August 2010

The N‐terminal sequences of two calf‐thymus non‐histone chromosomal proteins, HMG‐1 and HMG‐2, are compared. Both N‐terminal sequences are basic, and differ at only one position. This contrasts with the C‐terminal portion of HMG‐1 which we have previously shown to be high in acidic residues. There is no obvious sequence homology with any of the known sequences of the histones.
A STUDY OF PROTEINASE INHIBITION BY SIMULATION OF INHIBITOR REACTIVE SITE REGIONS: INTERACTION OF THE C‐TERMINAL UNDECAPEPTIDE OF OVINE PROLACTIN WITH SOME PROTEINASES
Authors: Rigbi Meir , Katcoff Don J.
Published: August 2010

The C‐terminal undecapeptide of ovine prolactin, H‐Leu‐Asn‐Cys‐Arg‐Ile‐Ile‐Try‐Asn‐Asn‐Asn‐Cys‐OH possesses several structural features common to protein proteinase inhibitors, yet has no inhibitor properties. The undecapeptide is completely hydrolysed by trypsin (Arg‐Ile bond) and by chymotrypsin (Tyr‐Asn bond), with a proteolytic coefficient of approximately 3,000 M‐1 sec‐1 and 240 M‐1 sec‐1 respectively. On the basis of these results, a consideration of entropy, and studies by other workers, we agree with the view of Nishino et al. that the best models for small synthetic peptides with inhibitor properties would be those naturally‐occurring inhibitors whose reactive site is located within a small disulphide loop.