Column chromatography of methylthiohydantoin derivatives of amino acids in the investigation of the primary structure of porcine pepsin

Summary 1. MTH--Aminobutyric acid has been synthesized and has been used as an internal standard in the column chromatography of MTH-(amino acid)s.2. The column chromatography of MTH-(amino acid)s has been used in the analysis of short peptides isolated from a thermolysin hydrolyzate of the B2 fragment of porcine pepsin.All-Union Scientific-Research Institute of the Genetics and Breeding of Industrial Organisms. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 770–775, November–December, 1974.     

Reaction of cis- and trans-3,4-epoxy-3-methylbicyclo-[4.1.0] heptanes with hydrogen halides

Conclusions The reaction of cis- and trans-3,4-epoxy-4-methylbicyclo[4.1.0]heptanes with hydrochloric and hydrobromic acids was studied. The reactions of the trans-epoxide yield products derived from rupture of the epoxide ring both on the secondary and tertiary carbon atoms. The reaction of the cis-epoxide results in preferential rupture of the tertiary bond with HC1 and the secondary bond with HBr.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 829–831, April, 1979.     

Rheological and phase behavior of polyamidobenzimidazole solutions under the effect of temperature and deformation

The viscosities and phase stabilities of solutions of rigid-chain polyamidobenzimidazole and its copolymer with poly(p-phenylene terephthalamide) in dimethylacetamide are investigated during their flow within wide temperature and shear-rate ranges. These systems are characterized by amorphous separation with the lower critical temperature of mixing. In the range of the phase-separation temperature, viscosity passes through a minimum owing to the formation of a microemulsion followed by gelation of the reversible system accompanied by its blurring due to uncompleted phase separation. The temperatures of phase separation and the temperatures of minimum viscosity for the investigated solutions decline with an increase in the polymer concentration and increase with an increase in the shear rate.     

Calcium peroxosilicates

Calcium peroxosilicates CaO·nSiO₂·xH₂O·yH₂O₂ (n = 1, 2) were synthesized by three methods: (1) the reaction of CaSiO₃·nH₂O (～7% CaSiO₃ suspension in water) with 50.7, 73.4, and 92% H₂O₂ at 0–5°C produced compositions CaSiO₃·6H₂O·2H₂O₂, CaSiO₃·2H₂O·4H₂O₂, and CaSiO₃·3H₂O·8H₂O₂, respectively; (2) the reaction of CaSiO₃·17H₂O with 50.7 and 73.4% H₂O₂ at 0–5°C produced the solvate CaO·2SiO₂·4H₂O·0.15H₂O₂; and (3) the reaction of CaSiO₃·3H₂O with H₂O₂ vapor at 5°C in the absence of anhydrone produced the solvate CaSiO₃·3.5H₂O·0.5H₂O₂. The products were characterized by X-ray powder diffraction, thermogravimetry, and IR spectroscopy.     

Cluster-based networks: 1D and 2D coordination polymers based on {MnFe2(μ3-O)}-type clusters

A straightforward approach to heterometallic Mn-Fe cluster-based coordination polymers is presented. By employing a mixed-valent μ(3)-oxo trinuclear manganese(II/III) pivalate cluster, isolated as [Mn(II)Mn(III)(2)O(O(2)CCMe(3))(6)(hmta)(3)]·(solvent) (hmta = hexamethylenetetramine; solvent = n-propanol (1), toluene (2)) in the reaction with a μ(3)-oxo trinuclear iron(III) pivalate cluster compound, [Fe(3)O(O(2)CCMe(3))(6)(H(2)O)(3)]O(2)CCMe(3)·2Me(3)CCO(2)H, three new heterometallic {Mn(II)Fe(III)(2)} cluster-based coordination polymers were obtained: the one-dimensional polymer chain compounds {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(2)]·0.5MeCN}(n) (3) and {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(2)]·Me(3)CCO(2)H·(n-hexane)}(n) (4) and the two-dimensional layer compound {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(1.5)]·(toluene)}(n) (5). Single-crystal X-ray diffraction analysis reveals a μ(3)-oxo trinuclear pivalate cluster building block as the main constituent in all polymer compounds. Different M:hmta ratios in 1-5 are related to the different structural functions of the N-containing ligand. In clusters 1 and 2, three hmta ligands are monodentate, whereas in chains 3 and 4 two hmta ligands act as bridging ligands and one is a monodentate ligand; in 5, all hmta molecules act as bidentate bridges. Magnetic studies indicate dominant antiferromagnetic interactions between the metal centers in both homometallic {Mn(3)}-type clusters 1 and 2 and heterometallic {MnFe(2)}-type coordination polymers 3-5. Modeling of the magnetic susceptibility data to a isotropic model Hamiltonian yields least-squares fits for the following parameters: J(1)(Mn(II)-Mn(III)) = -6.6 cm(-1) and J(2)(Mn(III)-Mn(III)) = -5.4 cm(-1) for 1; J(1) = -5.5 cm(-1) and J(2)(Mn(III)-Mn(III)) = -3.9 cm(-1) for 2; J(1)(Mn(II)-Fe(III)) = -17.1 cm(-1) and J(2)(Fe(III)-Fe(III)) = -43.7 cm(-1) for 3; J(1) = -23.8 cm(-1) and J(2) = -53.4 cm(-1) for 4; J(1) = -13.3 cm(-1) and J(2) = -35.4 cm(-1) for 5. Intercluster coupling plays a significant role in all compounds 1-5.     

CP/MAS NMR (13C, 15N, and 113Cd), thermal behavior, and sorption properties of cadmium Di-iso-butyldithiocarbamate. The gold(III)-binding species sorbed from solutions

The structure and thermal behavior of cadmium di-iso-butyldithiocarbamate (I) have been studied by solid-state ¹³C and ¹⁵N CP/MAS NMR and simultaneous thermal analysis (STA). The cadmium complex forms two crystalline polymorphs, ?? and ??. The structure of each of the polymorphs contains two structurally nonequivalent binuclear [Cd₂{S₂CN(iso-C₄H₉)₂}4] molecules. The STA data have shown the possibility of the ??-I ?? ??-I phase transition. Studying the thermal behavior of the complex has demonstrated that the end product of thermodestruction is a fine yellow-orange powder of CdS. The sorption properties of I have been studied with respect to gold(III) chloride solutions in 2 M HCl. It has been found that gold(III) is efficiently sorbed from strong acid solutions in the Au³⁺ concentration range 0.032?C3.220 mg/mL. On the basis of multinuclear (¹³C, ¹⁵N, and ¹¹³Cd) MAS NMR data, it has been demonstrated that the individual gold(III)-binding species in the sorption system is the ionic gold(III) cadmium-complex of composition [Au{S₂CN(iso-C₄H₉)₂}₂]₂[CdCl₄].     

LiF-LiBr-LiVO3-Li2SO4 four-component system

Phase equilibria in theLiF-LiBr-LiVO₃-Li₂SO₄ four-component system were studied using dif ferential thermal analysis (DTA). The eutectic composition (mol %) was determined as LiF, 20.0; LiBr, 45.7; LiVO₃, 25.7; Li₂SO₄, 8.6 with a melting temperature of 403°C and a specific enthalpy of melting of 216 kJ/kg.