Small-angle X-ray scattering study of the influence of solvent replacement (from H<Subscript>2</Subscript>O to D<Subscript>2</Subscript>O) on the initial crystallization stage of tetragonal lysozyme

The composition of lysozyme solutions in D₂O under conditions favorable for the formation of tetragonal crystals has been investigated at different protein concentrations by small-angle X-ray scattering using the synchrotron radiation. In addition to lysozyme monomers, dimeric and octameric species are found in the crystallization solutions; the octamer content increases with an increase in the protein concentration. A comparison of the data with those obtained under similar conditions but with H₂O used as a solvent has shown that the replacement of light water with heavy one leads to increase of octamer volume fraction in solution.     

Investigation of the Structure of Crystal-Forming Solutions of Potassium Dihydrogen Phosphate K(H2PO4) (KDP type) on the Basis of Modeling Precursor Clusters and According to Small-Angle X-Ray Scattering Data

Crystallography Reports - The potassium dihydrogen phosphate K(H2PO4) (KDP) cluster structures formed in aqueous solutions have been theoretically and experimentally investigated. Cluster modeling...     

Development of new methods for the synthesis of 2,3-bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate and its intermediates

Known methods for the synthesis of 2,3-bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate and its intermediates were investigated. New procedures were developed for the preparation of these compounds. 2,3-Bis(nitroxymethyl)-2,3-dinitrobutane-1,4-diol dinitrate was studied by X-ray diffraction.

     

Reductive Alkylation Causes the Formation of a Molten Globule-Like Intermediate Structure in <Emphasis Type="Italic">Geobacillus zalihae</Emphasis> Strain T1 Thermostable Lipase

A thermostable lipase from Geobacillus zalihae strain T1 was chemically modified using propionaldehyde via reductive alkylation. The targeted alkylation sites were lysines, in which T1 lipase possessed 11 residues. Far-UV circular dichroism (CD) spectra of both native and alkylated enzyme showed a similar broad minimum between 208 and 222 nm, thus suggesting a substantial amount of secondary structures in modified enzyme, as compared with the corresponding native enzyme. The hydrolytic activity of the modified enzymes dropped drastically by nearly 15-fold upon chemical modification, despite both the native and modified form showed distinctive α-helical bands at 208 and 222 nm in CD spectra, leading us to the hypothesis of formation of a molten globule (MG)-like structure. As cooperative unfolding transitions were observed, the modified lipase was distinguished from the native state, in which the former possessed a denaturation temperature (T _m) in lower temperature range at 61 °C while the latter at 68 °C. This was further supported by 8-anilino-1-naphthalenesulfonic acid (ANS) probed fluorescence which indicated higher exposure of hydrophobic residues, consequential of chemical modification. Based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, a small number of lysine residues were confirmed to be alkylated.     

Effect of particle size in preparative reversed-phase high-performance liquid chromatography on the isolation of epigallocatechin gallate from Korean green tea

To isolate epigallocatechin gallate (EGCG) of catechin compounds from Korean green tea (Bosung, Chonnam), a C18 reversed-phase preparative column (250x22 mm) packed with packings of three different sizes (15, 40-63, and 150 microm) was used. The sample extracted with water was partitioned with chloroform and ethyl acetate to remove the impurities including caffeine. The mobile phases in this experiment were composed of 0.1% acetic acid in water, acetonitrile, methanol and ethyl acetate. The injection volume was fixed at 400 microl and the flow rate was increased as the particle size becomes larger. The isolation of EGCG with particle size was compared at a preparative scale and the feasibility of separation of EGCG at larger particle sizes was confirmed. The optimum mobile phase composition for separating EGCG was experimentally obtained at the particle sizes of 15 and 40-63 microm in the isocratic mode, but EGCG was not purely separated at the particle size of 150 microm.     

Multiple intramolecular hydrogen bonds in 2,4‐di‐tert‐butyl‐6‐[N‐(2,6‐diisopropylphenyl)‐P,P‐diphenylphosphorimidoyl]phenol

The title compound, C₃₈H₄₈NOP, isolated from the reaction of (2‐diphenylphosphanyl‐4,6‐di‐tert‐butyl)phenol with 2,6‐diisopropylphenyl azide at 273 K, can act as an N,O‐bidentate ligand. Crystal structure analysis shows a deviation from ideal tetrahedral symmetry around the P atom. The molecule exists as a monomer in the solid state, whose conformation is stabilized via multiple intramolecular hydrogen bonds. Geometric parameters from both experimental and theoretical calculations are compared.     

Synthesis of ferrocenyl-containing heterocyclic derivatives of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin for sonodynamic therapy

The condensation of 1-(ferrocenylalkyl)pyrazole-3-carbaldehydes with 4′-aminotetraphenylporphyrin, followed by reduction with NaBH(OAc)₃ in 1,2-dichloroethane, provides a convenient method for the synthesis of 5-{4-[({1-[1-(ferrocen-1-yl)alkyl]-5-methyl-1H-pyrazol-3-yl}methyl)amino]phenyl}-10,15,20-triphenylporphyrins which exhibit pronounced cytotoxicity against Staphylococcus aureus under ultrasonic irradiation.