<p>A combined molecular modeling and molecular dynamics simulation was carried out to obtain an improved description of the yeast acetohydroxyacid synthase (AHAS) in aqueous solution. After a thorough homology modeling, the AHAS catalytic dimer was subjected to a molecular dynamics (MD) simulation to analyze its behavior and optimize its geometry. The AHAS 3D molecular structure was analyzed according to the number of salt bridges and hydrogen bonds formed. During 20 ns of MD simulation, an average fluctuation of 3.9 Å was obtained. The cofactor thiamine diphosphate makes a relevant contribution to the system stability; this hypothesis was confirmed by the decrease in the average fluctuation of 0.3 Å. Moreover, the Ramachandran plot revealed no denaturation framework during the time of the simulation.</p>

Os compostos hidrotris(2-mercaptotiazolil)borato de potássio, KMt, (1), e hidrotris(2-metimazolil)borato de potássio, KTm, (2), foram preparados ao se reagir a amina tiol correspondente com KBH4. Foram caracterizados por métodos espectroscópicos e análise elementar. As estruturas no estado sólido de KMt.4H2O e do composto 2 foram determinadas por análises de difração de raios-X. A maior maciez do ânion em KMt.4H2O, em comparação com 2, é indicada pela ausência de interação entre ele e o cátion, que possui moléculas de água em sua esfera de coordenação. Em KMt.4H2O a geometria em torno do íon potássio é octaédrica distorcida e em 2, pirâmide de base quadrada distorcida. Em 2 o íon potássio está coordenado a dois átomos de enxofre dos anéis de um mesmo ânion e a três outros átomos de enxofre pertencentes a unidades KTm vizinhas. Ambos os compostos possuem uma estrutura polimérica.

Potassium hydrotris(2-mercaptothiazolyl)borate, KMt, (1) and potassium hydrotris(2-methimazole), KTm, (2), were prepared by reacting the appropriate amine thiol with KBH4. They were characterized by spectroscopic methods and elemental analysis. Solid state structures of KMt.4H2O and compound 2 were determined by X-ray diffraction analyses. The softer nature of the anion in the former as compared to 2 is indicated by the lack of interaction of the anion with the cation, that has water molecules in its coordination sphere. In KMt.4H2O the geometry around the potassium cation is distorted octahedral and in 2, distorted square pyramidal. In 2 the potassium ion is coordinated to two sulfur atoms of one hydrotris(methimazole)borate unit and to other three sulfur atoms belonging to neighboring KTm units. Both compounds have a polymeric structure.

The crystal and molecular structures of (E)-1-(3,4,5-trimethoxyphenyl)-2-nitroethene (1), C11H13NO5, Mr = 239.2, and (E)-1-(3,4,5-trimethoxyphenyl)-2-nitropropene (2), C12H15NO5, Mr = 253.3, were determined by X-ray diffraction. Compound 1: monoclinic, space group P21/c, a = 7.429(2), b = 9.828(3), c = 32.766(2) Å, <FONT FACE=Symbol>b</FONT> = 95.65(2)°, V = 2381(1) Å3, Z = 8. Compound 2: monoclinic, space group P21/c, a = 8.888(3), b = 13.650(3), c = 10.369(3) Å, <FONT FACE=Symbol>b</FONT> = 94.04(2)°, V = 1255(1) Å3, Z = 4. Compound 1 exhibits no unusual structural features. Compound 2 shows a side chain out of the ring plane and with expanded valence angles

Las estructuras cristalinas y moleculares de (E)-1-(3,4,5-trimetoxifenil)-2-nitroeteno (1), C11H13NO5, Mr = 239,2 y (E)-1-(3,4,5-trimetoxifenil)-2-nitropropeno (2), C12H15NO5, Mr = 253,3, fueron determinadas por difracción de rayos X. El compuesto 1 es monoclínico, grupo espacial P21/c, a = 7,429(2), b = 9,828(3), c = 32,766(2) Å, <FONT FACE=Symbol>b</FONT> = 95,65(2)°, V = 2381(1) Å3, Z = 8. El compuesto 2 es monoclínico, grupo espacial P21/c, a = 8,888(3), b = 13,650(3), c = 10,369(3) Å, <FONT FACE=Symbol>b</FONT> = 94,04(2)°, V = 1255(1) Å3, Z = 4. El compuesto 1 no presenta rasgos inusuales en su estructura molecular. El compuesto 2 tiene la cadena lateral fuera del plano del anillo y con los ángulos de valencia expandidos