A convenient preparation of pentaaquanitrosylchromium(2+) sulfate: The crystal structure revisited

The complex pentaaquanitrolsylchromium(2+) sulfate, [Cr(OH₂)₅(NO)]SO₄ has been prepared in a high yield by the hydrolysis of [Cr(NCCH₃)₅(NO)](BF₄)₂ in dilute sulfuric acid. Crystals of [Cr(OH₂)₅(NO)]SO₄ · H₂O have been grown and characterized by X-ray crystallography. Continuous photolysis of [Cr(NCCH₃)₅(NO)]²⁺ in acetonitrile solution with 404 nm light results in a release of NO with the quantum yield Φ = 0.55 mol einstein⁻¹ at 298 K with the resulting solvated Cr²⁺ ion being trapped by molecular dioxygen present in the solution.     

A convenient synthesis of dinorbile acids: oxidative hydrolysis of norbile acid nitriles

We report a convenient method for the synthesis of dinorbile acids (23,24-dinor-5beta-cholan-22-oic acids, pregnane-20-carboxylic acids) in fair to good yields from norbile acid nitriles in one step by oxidative hydrolysis with oxygen in the presence of potassium-t-butoxide. The method results in stepwise overall removal of two carbon atoms in bile acid side chains in two steps. Dinorbile acids corresponding to several common bile acids have been prepared and their structures confirmed by spectroscopic methods. This simple method for synthesis of dinorbile acids may facilitate their study metabolically.     

A simple and convenient preparation of succinic semialdehyde

Succinic semialdehyde (SSA) is prepared from 4-pentenoic acid by ozonolysis and reductive decomposition of the formed ozonide (40–50% yields). Aqueous solutions of SSA are obtained by water extraction from ethyl acetate solution of the mixture of reaction. Quantitative estimation of SSA was performed enzymatically by means of SSA dehydrogenase.     

A convenient manual trinitrobenzenesulfonic acid method for monitoring amino acids and peptides in chromatographic column effluents.

The trinitrobenzenesulfonic acid (TNBS) method of R. Fields (1971, Biochem. J., 124, 581–590) has been modified for the manual detection of amino acids and peptides in chromatographic column effluent by changing the reaction conditions to 1 mm TNBS in 0.4 m potassium borate buffer, pH 9.2, at room temperature for 30 to 50 min. The reaction with amines and the spontaneous hydrolysis of TNBS are stopped by neutralization to pH 6.25 with sodium monobasic phosphate (0.33 m). Sodium sulfite (3 mm) is added to increase the absorptivity of the product. The TNBS reagent blank is less than 0.100 A₄₂₀ after 50 min of reaction. Since the ΔA₄₂₀ of the reagent blank is ～0.002/min before quenching the reaction, and zero afterward, the time required for reaction and for absorbance measurements need not be controlled precisely. Alkaline hydrolysis of peptides is carried out prior to detection to increase the sensitivity of the method. This procedure is convenient for the manual determination of 5 to 100 nmol of amino acids in the 50–100 samples required to define a chromatographic elution profile.     

Phosphonopyruvic acid: A probable precursor of phosphonic acids in cell-free preparation of Tetrahymena.

1. In cell-free preparations of Tetrahymena, doubly labelled [32P]phosphoenol-[3-14C]pyruvate gives rise to 2-aminoethylphosphonate and 2-amino-3-phosphonopropionate, labelled with the two isotopes in the same ratio as the starting compound. The result is consistent with an intra-molecular rearrangement of phosphoenolpyruvate in the biosynthetic sequence of carbon-phosphorus bond formation. 2. Incubation of [32P]phosphoenolpyruvate with the same preparation, followed by treatment with 2,4-dinitrophenylhydrazine, yielded labelled hydrazones. When these were subjected to hydrogenolysis, the radioactivity was recovered in 2-aminoethylphosphonate and 2-amino-3-phosphonopropionate, suggesting that 2-phosphonoacetaldehyde and 3-phosphonopyruvic acid were probable precursors of the aminoalkylphosphonic acids. 3. Radioactivity from 2-amino-3-phosphono-[3-14C]propionic acid was incorporated into 2-aminoethylphosphonic acid, but incorporation of the radioactivity into lipids was negligible.     

X-ray studies of water structure in 2 Zn insulin crystal

The water structure of rhombohedral 2 Zn insulin crystal which contains about 280 water molecules and 0.55-0.60 mol citrate molecules per dimer has been studied by X-ray crystallographic refinement with 1.1 A resolution data. Atomic parameters of 83 fully occupied and 258 partially occupied water molecules and 0.3 mol of citrate were obtained. Full matrix least-squares method with isotropic temperature factor was used for the refinement of partially occupied water molecules. The water molecules in this crystal exist in one of the three states: fully occupied water, partially occupied water and water continuum, and a schematic model of water structure in protein crystal was proposed. The flexibility of water molecules is described.     

Intermolecular interactions and water structure in a condensed phase B-DNA crystal

By controlled dehydration, the unit cells of dodecamer DNA–drug crystals have been shrunk from 68 000 (normal state) to 60 000 (partially dehydrated intermediate state) to 51 000 ų (fully dehydrated state), beyond which no further solvent loss occurs. The total solvent content in the normal crystals is ~40% by volume, reducing to ~20% in the fully dehydrated phase. The 25% reduction in cell volume induced a dramatic enhancement in the resolution of the X-ray diffraction data (from 2.6 to beyond 1.5 Å). We have determined the structures of the normal, partially dehydrated and fully dehydrated crystals. Details of the ligand binding have been presented in the preceding article. The present paper describes the unique features of the structure of the fully dehydrated phase. This structure was refined with 9015 unique observed reflections to R = 14.9%, making it one of the most reliable models of B-form DNA available. The crystals exist as infinite polymeric networks, in which neighbouring dodecamer duplexes are crosslinked through phosphate oxygens via direct bonding to magnesium cations. The DNA is packed so tightly that there is essentially only a single layer of solvent between adjacent molecules. The details of the crystal packing, magnesium bridging, DNA hydration and DNA conformation are described and compared with other experimental evidence related to DNA condensation.     

A convenient preparation of the side-chain lactone ring of a withanolide precursor

Condensation of C22 and C21 steroidal aldehydes with ethyl 4,6-dimethyl-2-oxo-2H-pyran-5-carboxylate 1 in alkaline medium, followed by decarboxylation, provides a simple route to the alpha, beta-unsaturated side-chain delta-lactone synthesis for a classical withanolide precursor.     

A convenient preparation of 6-oligo(lactic acid)cyclomaltoheptaose as kinetically degradable derivative for controlled release of amoxicillin

6-Oligo(lactic acid)cyclomaltoheptaose (6-OLA-βCD) with an average substitution of about 7.0 lactic acid units was prepared as a new water-soluble cyclomaltoheptaose (βCD) derivative (solubility of about 70.7-fold that of βCD), based on the ring-opening polymerization of 3,6-dimethyl-1,4-dioxane-2,5-dione (lactide). The product was characterized by ¹H NMR, ¹³C NMR, IR, and MS spectroscopy. The complexation of amoxicillin with 6-OLA-βCD was found to be much stronger than that with βCD at first, and then 6-OLA-βCD was shown to decompose moderately into βCD and lactic acid. 6-OLA-βCD might be greatly valuable in a controlled release system for Amoxicillin (AMX).