Principles of modeling in the study of conformations of histones

A study has been made by the CD method of the conformational potentialities of the polypeptides (Gly-Lys-Gly)_n and (Ala-Lys-Ala)_n and fragments of the terminal sections of histones H4 (the sequence 1–16), H2B (1–21), and H1 (152–184), and they have been used as models of histones in complex formation with DNA under various conditions of the medium.V. I. Nikitin Institute of Chemistry, Tadzhik SSR Academy of Sciences, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 391–398, May–June, 1989.     

Spin-label study of the conformational states of polypeptide models of histones

The conformational states of the regular polypeptides (Gly-Lys-Gly)_n, (Ala-Orn-Gly)_n, and (Ala-Orn-Ala)_n have been studied by the spin-label method. Their behavior in solutions of guanidine hydrochloride and urea and in solutions of salts of bivalent metals does not contradict the presence of an extended levohelical conformation in their polypeptide chains. In CaCl₂ (5 N) solutions the polypeptides exhibit aggregation properties. A study of the behavior of the poly peptide at these temperatures has shown that with a rise in temperature there is a monotonic change in the structures of the polypeptide chains that is characteristic for a conformation of the polyproline-II type. Differences have been observed in the behavior of glycine-and alanine-containing polypeptides in the presence of sodium dodecyl sulfate with a change in the temperature.V. I. Nikitin Institute of Chemistry of the Academy of Sciences of the Tadzhik SSR, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 218–222, March–April, 1986.     

Study of the structure and stability of compounds PF n,n=1–5, and their anions by the density functional method

The electronic and geometrical structure of phosphorus fluorides PF_n, n = 1–5, and their singly-charged negative ions was calculated using the density functional method. Both the ground and low-lying excited states of the two series were considered. The structural parameters of neutral radicals PF₂, PF₄, and their anions were obtained for the first time. The adiabatic and vertical electron affinities (EA) of the neutral phosphorus fluorides, and the first ionization potentials of the anions were calculated. According to the calculation results, all the phosphorus fluorides have positive EA_ad, except for PF₃, which has an EA of about zero, and requires further investigation. The dissociation energies of both the neutral and negatively charged phosphorus fluorides were calculated through different channels. All the PF_n and PF _n ^– , n = 1–5, are stable in the gaseous phase. The PF^–, PF ₂ ^– , PF ₃ ^– , and PF ₅ ^– anions have excited states which are stable with respect to both the splitting off of an outer electron and to dissociation.Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2219–2232, October, 1992.     

Synthesis of regular polypeptides including lysine, proline, and alanine residues

Conclusions Polypeptides of the following sequences have been obtained: -Lys-Pro-,-Lys₂-Pro-, -Lys₃-Pro-,-Lys-Pro₂-, and -Lys-Ala-, with molecular weights of from 1000 to 14,000. It has been established that the use of pentachlorophenyl esters for polymerization in place of 2,4,5-trichlorophenyl esters leads to a considerable increase in the molecular weights of the polypeptides.Institute of Chemistry, Academy of Sciences of Tadzhik SSR. Institute of Molecular Biology, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 210–213, March–April, 1974.     

Synthesis and X-Ray Crystal Structures of Fe2Ru(CO)12−n (CNBu t ) n and FeRu2(CO)12−n (CNBu t ) n (n=1, 2)

The clusters Fe₂Ru(CO)_12–n (CNBu ^t ) _n (3, n=1; 4, n=2), FeRu₂(CO)_12–n (CNBu ^t ) _n (5, n=1, 6, n=2) and FeRu₂(CO)₁₁(CNCy) (5a) have been prepared by direct substitution from the parent carbonyl precursors Fe₂Ru(CO)₁₂ (1) and FeRu₂(CO)₁₂ (2). All compounds have been characterized spectroscopically and clusters 3, 4, 5, and 6 by single crystal X-ray determinations. In all cases, the isonitrile ligands adopt axial or pseudo-axial positions on a ruthenium atom. The structures of 3–5 are very similar to their parent clusters, but the extent of metal framework disorder is significantly less. Cluster 6 adopts the same C _2v Fe₃(CO)₁₂ type structure as 4, and thus differs markedly from the parent compound 2, which has a D ₃ structure .     

Crystal and molecular structures of cyclohepta(p-phenylene sulfide) and cycloocta(p-phenylene sulfide)

The crystal structures of two cyclic poly(phenylene sulfides) have been determined. The structure of the (p–C₆H₄–S)₁ heptamer contains four crystallographically independent molecules, which are related in pairs by approximate symmetry centers. The molecules in the pairs have similar conformations and form alternating monomolecular layers parallel to the ab plane. The molecule of the (p–C₆H₄–S)₈ octamer has S₄ crystallographic symmetry (a saddle-shaped conformation), and solvent molecules are found in the intramolecular cavities in the crystal.A. N. Nesmeyanov Institute of Organometallic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 125–132, March–April, 1991.     

X-Ray diffraction study of solid-state photoisomerization products [Co(NY3)5NO2]XY (X,Y = Cl,Br, I,NO3)

Complexes [Co(NH₃)₅NO₂]XY and [Co(NH₃)₅ONO]XY (X,Y=Cl, Br, I, NO₃) have been studied by the X-ray diffraction method. The unit cell parameters were refined for the nitro isomers and determined for the nitrito isomers. We have analyzed changes in the latter arising during the nitro-nitrito photoisomerization and the reverse nitrito-nitro thermal isomerization. The topotaxial character of the structural rearrangement has been shown. The X-ray diffraction data obtained were compared with IR and kinetic data.Institute of Solid State Chemistry and Processing of Mineral Raw Materials, Siberian Branch, Russian Academy of Sciences. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 128–140., July–August, 1993.Translated by T. Yudanova     

Optimization of the method of isolating (25R)-spirost-5-ene-3β,17α-diol (pennogenin) from plant material

The method for the acid hydrolysis of pennogenin glycosides with the aim of isolating the native aglycon has been optimized. The highest yield of pennogenin (49.5% of its amount in the plant material) is given by hydrolysis with 1 N H₂SO₄ in 96% ethanol at 100°C for 3 h.Pacific Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 115–119, January–February, 1987.     

The OsX n Coordination Polyhedra (X = O,S, Se,Te) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform a crystal-chemical analysis of compounds whose structures contain Os atoms surrounded by chalcogen atoms. Depending on the valence state, Os atoms bind four to seven X atoms (X = O, S, Se, Te) forming OsX _n coordination polyhedra which can be tetrahedra (n = 4), trigonal bipyramids or square pyramids (n = 5), octahedra (n = 6), or pentagonal bipyramids (n = 7). In some compounds, pairs of OsO₆ octahedra share edges to form Os–Os bonds. The influence of the Os valence state and the nature of the chalcogen atom on the composition and structure of the [Os _a X _b ] groups is discussed. On the basis of analysis of the crystal-structural data from the standpoint of the 18-electron rule, dependences of the Os–O and Os–Os bond orders on the bond lengths are proposed.     

Comparative study of the cytotoxins of the venom of the central asian cobraNaja naja oxiana by the intrinsic-fluorescence method

The intrinsic fluorescence of cytotoxin V_C1 and V_C5 from the venom of the Central Asian cobra due to the tyrosine residues and differing with respect to quantum yield for these two polypeptides because of the nonidentity of the microenvironments of the tyrosyl residues has been measured and characterized. The dependence of the quantum yield on the pH and the temperature also indicate this nonidentity.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 226–228, March–April, 1986.     

Template synthesiS: Geometrical and electronic structures of the Fe nitrosyl complex formed by bis(S-methylisothiosemicarbazone)-2,4-pentandione

Sodium acetylacetonate reacts with S-metliylisothiosemicarbazidium nitrate and Fe(NO₃)₃ · 9H₂O in ethanol to make [Fe(HL)NO]NO₃, in which H₃L is bis(S-methyl-isothiosemicarbazone)-2,4-puntandione. The [Fe(HL)NO]⁺ cation has a square pyramidal structure with the HL^2- arranged around the central ion in the basal plane and the nitrogen atom of the NO group in the apical position, with the iron atom diverging from the plane of the base of the pyramid by 0.477 Å. The FeN0 moiety has a linear structure (FeNO = l72.7°). XRD, IR, and Mössbauer spectroscopy have been combined with calculations on the electronic structure to demonstrate that the Fe-NO bond is covalent.Chemical Institute, Academy of Sciences of Moldavian SSR. Applied Physics Institute, Academy of Sciences of the Moldavian SSR. Kishinev. Institute of Crystallography, Academy of Sciences of the USSR. Kurnakov Institute for General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No, 3, pp. 376–381, May–June, 1991. Original article submitted February 18, 1991.     

Synthesis of polypeptides with the sequences-Gly-Gly-Ala-, -Gly-Gly-Lys(Tos)-, and-Gly-Gly-Glu(OCH3)- and the influence of triethylamine on the degree of their polycondensation

Conclusions The synthesis of polytripeptides with the sequences -Gly-Gly-Ala-,-Gly-Gly-Lys(Tos)-, and -Gly-Gly-Glu(OCH₃)-having molecular weights of 11,000, 39,000, and 3000, respectively, have been effected.Institute of Molecular Biology, Academy of Sciences of the USSR. Institute of Chemistry, Academy of Sciences of the TadzhSSR, V. I. Lenin Tadzhik State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 206–210, March–April, 1974.     

Search for regular polypeptides possessing esterase properties. I. Polypeptides containing tyrosine and glutamic acid residues

An investigation has been made of the catalytic properties in relation to the hydrolysis of p-NPA of six polypeptides of regular structure: H-[Glu-Tyr]_n-OH (1), H-[Glu₂-Tyr]_n-OH (2), H-[Glu-Tyr₃]_n-OH (3), H-[Glu₃-Tyr]_n-OH (4), H-[Glu₃-Tyr]_n-OH (5), and H-[Glu-Tyr₂]_n]-OH (6). It has been shown that polypeptides (I), (III), and (IV) catalyze the hydrolysis of p-NPA (p-nitrophenyl acetate). An enzyme-like type of catalysis has been found. Some catalytic characteristics have been calculated and the dependence of the rate of hydrolysis on the pH of the medium, the temperature, and the concentration of p-NPA have been discussed. The structures of the catalytically active and catalytically inactive polypeptides have been studied by the circular dichroism method. It has been shown that under conditions in which the catalytic properties of polypeptides are shown to the maximum degree there is a structure of the random coil type. The catalytic activity falls or disappears completely when ordered fragments of the -helix and -structure types appear in the structure. It has been found that polypeptide (I) possesses the maximum catalytic activity. It exceeds the activity of a copolymer of the same amino acids by an order of magnitude.Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow. Tadzhik State University, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 687–699, September, October, 1979.     

Synthesis of regular polypeptides including L-lysine and glycine

Conclusions The synthesis of two regular polypeptides with the composition (—Gly—L-Lys—Gly)_n and (—L-Lys—L-Lys—Gly—)_n with molecular weights of 250 and 5000 has been effected.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 459–462, 1970The bulk of this work was carried out in the Protein Chemistry Laboratory of the Institute of Organic Chemistry, AS USSR.     

Some bactericidal properties of oligopeptides and regular polypeptides including lysine and ornithine residues

Summary Oligopeptides and polypeptides of the sequences Lys₆-, Ala-Lys₄-Ala, Lys₈-, Orn₂-Ala₂-, Lys₃-Pro-, Lys₃-Gly-, Orn₃-Gly-, Lys-Pro-, Lys-Pro₂-, Lys₂-Pro-, Lys₃-Ala- possess bactericidal properties in relation to a strain of the bacteriumStaphylococcus aureus.It has been shown that with an increase in the amount of lysine and ornithine residues in the polypeptide chain the bactericidal properties increase; proline residues play a fundamental part in the manifestation of these properties.Institute of Molecular Biology, Academy of Sciences of the USSR, Moscow. Institute of Chemistry, Academy of Sciences of Tadzhik SSR, Dushanbe. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 130–133, January–February, 1978.     

Preparation and properties of the layered organic derivatives of γ-zirconium phosphate,Zr(CH3−(OCH2CH2)n−OPO3) (HPO4) (n=1–3)

New kinds of organic derivatives of layer structured -zirconium phosphate Zr(HPO₄)₂·2H₂O are prepared by the exchange of the interlayer phosphate groups with phosphoric ester groups having oxyethylene chains, CH₃–(OCH₂CH₂)_n–OPO₃ ^2– (n=1–3). Half of the interlayer phosphate groups are exchanged topochemically, the oxyethylene chains being grafted onto the phosphate layers through the ester bonds in the resulting derivatives. The derivatives behave like crown ethers, and form complexes with alkali salts of soft base anions such as SCN^– and I^–. Alkali salts of hard base anions such as Br^– and NO₃ ^– do not form complexes with the derivatives. The alkali iodide complexes of the organic derivatives can be used for the halogen exchange reaction. n-Butyl bromide is converted into n-butyl iodide in the presence of the alkali iodide complexes. The reactivities for the halogen exchange reaction increase with the number of the oxyethylene units.     

Anomeric effect and structure of Si(OH)4 and related molecular systems

By the ab initio SCF MO LCAO method in a 3-21G basis and in the valence approximation of MNDO, the structure and conformation of Si(OH)₄ and related systems have been investigated. The results are judged from the standpoint of the anomeric effect. Model structures are proposed for the buildup of extended silicate systems.Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 482–485, July–August, 1991. Original article submitted October 12, 1990.     

Phosgene‐free synthesis of polypeptides: Useful synthesis for hydrophobic polypeptides through polycondensation of activated urethane derivatives of α‐amino acids

We report a useful synthetic method of polypeptides using a series of urethane derivative of α‐amino acids (l ‐leucine, l ‐phenylalanine, l ‐valine, l ‐alanine, l ‐isoleucine, l ‐methionine), which are readily synthesized by N‐carbamoylation of tetrabutylammonium salts of α‐amino acids with diphenyl carbonate. Heating these urethane derivatives in N,N‐dimethylacetamide in the presence of n‐butylamine successfully gave the corresponding polypeptides with well‐defined structures through polycondensation with the elimination of phenol and CO₂. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry investigation showed that the resulting polypeptides had an n‐BuNH₂‐incorporated initiating end and an amino group at propagating end. These results strongly indicated that primary amines served as an initiator in this polycondensation system. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3726–3731     

Synthesis of thienylhydrogermanes and their transformations in the presence of di(tert-butyl) peroxide

A method was developed for the synthesis of thienylhydrogermanes R_nGeH_4–n (where R=2-thienyl, n=1–3), involving the reduction of the corresponding ethoxygermanes by lithium aluminum hydride under the conditions of phase-transfer catalysis. The transformations of thienylhydrogermanes under the influence of di(tert-butyl) peroxide were studied. Features of the mass-spectrometric behavior of thienylethoxygermanes were analyzed.Latvian Institute of Organic Synthesis, Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 198–201, February, 1997.