[Experience of mesenteric sector fixation in mesenteric torsion treatment].

Objective: The preliminary results was reported regarding the treatment of mesenteric torsion by mesenteric fixation in the last decade, especially preventing recurrence of mesenteric torsion by mesenteric fan-shaped fixation. Methods: We selected 12 patients who received emergency operation in Chongqing Hospital of the First Affiliated Hospital of Guangzhou University of Chinese Medicine from December 2010 to March 2022. All of them were made a definite diagnose of mesenteric torsion by the preoperative CT scan or exploratory laparotomy. The recurrence of mesenteric torsion will be prevented by taking the operation of mesenteric fan-shaped fixation. This technique is suitable for the patient who is suffering total mesenteric torsion, but enteric necrosis is excluded affirmatively. The operation is consists of the following progress: (1) Exploratory laparotomy to check for necrosis of the bowel and for lesions other than torsion. (2) Mesenteric torsion derotation.(3) Mesenteric linear fixation; the right posterior lower border of the small mesentery (terminal ileal mesentery) is intermittently sutured to the posterior peritoneum of the right lower quadrant to increase the width of the base of the small mesentery. (4) Mesenteric fan-shaped fixation, which is fan-shaped to the lower left and fixed in the posterior peritoneum, shortening the length of the mesentery and further increasing the width of the mesentery and posterior peritoneal fixation. Results: A total of 12 patients with mesenteric torsion were treated by operation for 15 times in all. Among them, 3 cases received resection of most small bowel were performed without recurrence; 3 patients received only derotation for a total of 4 times, 2 cases recurred, 1 of them recurred twice; 4 cases underwent derotation and mesenteric linear fixation,and 1 case recurred. Four patients with derotation and mesenteric fan-shaped fixation recovered well without recurrence. Conclusion: Mesenteric fan-shaped fixation may be an effective operative type to reduce or avoid postoperative recurrence of mesenteric torsion.

Crystallization and preliminary X-ray studies of allophycocyanin from red alga Porphyra yezoensis.

Allophycocyanin from red alga Porphyra yezoensis has been crystallized in three crystal forms. Form 1 crystals with space group P4132 or P4332 and cell parameters a = 286 A, alpha = 90 degrees were obtained by using isopropanol as precipitant. These crystals did not diffract beyond 5.8 A and could not be used in structure analysis. Form 2 crystals were obtained when crystallization conditions were slightly changed by adding 0.2 M magnesium chloride. The space group of form 2 was not determined because it was difficult to get large single crystals. Form 3 crystals were obtained by using ammonium sulfate as precipitant. The space group of form 3 is R32 with cell dimensions a = b = 105.3, c = 189.4 A and one alpha beta unit in the asymmetric unit. These crystals diffract up to 2.06 A resolution and are suitable for structure determination by molecular-replacement methods.

Structure of monomeric porcine DesB1-B2 despentapeptide (B26-B30) insulin at 1.65 A resolution.

Insulin has a concentration of 10(-8)-10(-11) M in the blood which ensures that it circulates and exerts its physiological functions in vivo as a monomer. The crystal structure of monomeric porcine desB1-B2 despentapeptide (B26-B30) insulin (DesB1-2 DPI) with M(r) = 4934 Da has been determined at 1.65 A resolution using the molecular replacement method. A structural comparison between DesB1-2 DPI and 2Zn insulin reveals that the conformation of DesB1-2 DPI is more similar to molecule I than molecule II of 2Zn insulin. The remarkable conformational difference between B25-Phe in DesB1-2 DPI and B25-Phe in despentapeptide (B26-B30) insulin (DPI) indicates that the residue B25-Phe possesses great flexibility and mobility.

Crystal structure of R-phycoerythrin from Polysiphonia urceolata at 2.8 A resolution.

The structure of R-phycoerythrin (R-PE) from Polysiphonia urceolata was determined at 2.8 A resolution. The crystals belong to space group R3 with unit cell dimensions of a = b = 189.8 A, c = 60.1 A. The subunit composition of R-PE is (alpha 2 beta 2)3 gamma. The three-dimensional structure of R-PE was solved by the multiple isomorphous replacement method. After several cycles of model building and refinement, the crystallographic R-factor of the final model is 18.0% with data from 10.0 to 2.8 A resolution. The four phycoerythrobilin chromophores alpha 84, alpha 140a, beta 84 and beta 155 in an (alpha beta) unit are each covalently bound to a cysteine residue through ring A. The phycourobilin chromophore is bound to cysteine beta 50 by ring A and bound to cysteine beta 61 by ring D. The ring A and ring D of phycourobilin deviate from the conjugate plane formed by ring B and ring C and the four rings form a boat-shaped structure. R-PE contains a 34 kDa gamma subunit that is assumed to lie in the central channel of the molecular disc (alpha 2 beta 2)3. The energy transfer and relationship between cysteine residues and chromophores are discussed.

Purification and crystal growth of F1-ATPase from pig heart mitochondria.

A method has been evolved toward the aim of getting suitable crystals for high resolution of structural analysis of F1-ATPase by X-ray crystallography. The different conditions for crystal growth of ATPase that were isolated and purified by different methods from pig heart mitochondrial ATP synthase had been compared and screened. A simple method for purification of F1-ATPase was adopted. The F1-ATPase is released with chloroform from submitochondrial particles. Then it was treated with fractional precipitation of (NH4)2SO4 and finally was further purified by employing the sephadex G 200 column. The crystals of F1-ATPase were usually obtained after a few months. They appeared to have uniform morphology of tetrahedron. They diffracted to a resolution of 7A. The diffraction data were collected on the XRD-100 Siemens Area Detector. According to a total of 240 frames, the cell parameters obtained are a = b = 147 A, c = 208 A, alpha = beta = gamma = 90 alpha, the probable space group is P4 or its antipode. The reproducibility of this method for crystallization of F1-ATPase is good.

A proposed interaction model of the insulin molecule with its receptor.

Based on the extensive structural comparisons among the determined structures of the different species and crystal forms of insulin and its derivatives in our laboratory, it was suggested that the binding interaction with the receptor molecule should take place mainly on an amphipathic surface of the insulin molecule. In the middle of this amphipathis surface, there was a hydrophobic surface with an area of about 150 A2, while the polar and charged groups distributing around the hydrophobic surface constructed a hydrophilic zone. The hydrophobic surface was usually covered by the extended B-chain C-terminal peptides with great mobility. The angle between the proposed binding interaction surface and the surface of dimerization was about 20 degrees. The results from studies on structures of A1-(L-Trp) insulin and A1-(D-Trp) insulin confirmed the interaction mechanism model we proposed.

The possible mechanism of binding interaction of insulin molecule with its receptor.

Detailed structural comparisons and investigation of DPI, 2 Zn insulin and some other derivatives of insulin were performed by the least-squares superimposition technique and the graphics technique. It is pointed out in this paper that the binding interaction with the receptor molecule should take place mainly on an amphipathic surface of the insulin molecule. In the middle, there is a hydrophobic surface with an area of about 150 A2 consisting of many hydrophobic residues; while the polar or charged groups distributing around the hydrophobic surface construct a hydrophilic zone. The hydrophobic surface is usually covered by the extended B-chain C-terminal peptides with great mobility and protected from the solvent molecules. The angle between the amphipathic surface and the surface of dimerization is about 20 degrees. The results from the detailed structural comparison between Al-(L-Trp) insulin and Al-(D-Trp) insulin have provided a very good explanation to their great difference in biological activity, and confirmed our proposed binding interaction model of the insulin molecule with its receptor as well.

Preliminary crystallographic analysis of deshexapeptide (B25-B30) insulin.

Satisfactory single crystals of deshexapeptide (B25-B30) insulin for X-ray crystal structure analysis have been grown in citrate buffer by the method of hanging-drop gas phase diffusion. The crystal belongs to the monoclinic system with space group C2. The unit cell constants are a = 42.6 A, b = 37.9 A, c = 27.2 A, beta = 125.4 degrees and there is only one molecule of deshexapeptide insulin in an asymmetric unit.

Studies on the crystal structure of A1-(D-Tryptophan) insulin.

We have determined the crystal structure of A1-(D-Trp) insulin and discovered that it belongs to the trigonal system with space group R3. The parameters of the unit cell are a = b = 78.6 A, c = 50.0 A. A set of data for half a sphere reciprocal space to a spacing of 2.2 A were collected. The model was adjusted and refined by using a step-by-step approach and a stereochemically-restrained least squares program, assisted by manual revision based on the difference Fourier maps, to a final R-factor of 0.218. The main and side chains of both A1-D-Trp residues in the asymmetric unit are well ordered. The packing of A1-(D-Trp) insulin in the unit cell, the conformational differences with other insulin structures and its structure and function relationship have also been discussed.

Studies on the crystal structure of A1-(L-tryptophan) insulin at 2.1 A resolution.

In order to study the biological effect of alterations to the N-terminus of the insulin A-chain, we have determined the crystal structure of A1-(L-Trp) insulin and discovered that it belongs to the trigonal system with space group R3. The parameters of the unit cell are a = b = 80.3A, c = 37.5A. The model was adjusted and refined by using a stereochemically-restrained least squares program, assisted by manual revision of the model based on the difference Fourier map, to a final R-factor of 0.195. The main and side chains of both A1-(L-Trp) residues in the asymmetric unit are well ordered. It was found that the A1-Trp residue of molecule I occupied two distinct positions. We have proposed from the results of the three-dimensional structure that the 4-zinc insulin hexameric form is a stored state of insulin molecules in a conformation of low activity. The structural details of the insulin molecule and its structure and function relationship have also been discussed.

Molecular structure and absolute configuration of suberogorgin.

In the present paper it is reported that the molecular structure and absolute configuration of poisonous suberogorgin are determined by using X-ray diffraction method. The crystal of suberogorgin belongs to orthogonal system with space group D4(2)-P2(1)2(1)2(1). The crystallographic parameters are: a = 16.135A, b = 13.189A, c = 12.901A, Z = 8. The initial model of the crystal structure was solved by the direct method. The refinement of the structure parameters was carried out by using the least square method and led to a final R-factor of 0.056. In accordance with the molecular structure of suberogorgin mentioned above, the solvent effect of NMR has been further discussed and the relationship between the molecular structure of suberogorgin and its toxicity has also been preliminarily investigated.

Molecular structure and absolute configuration of the diterpene lactone, praelolide.

Praelolide is a new compound which was isolated out from the gorgonian, Menella praelonga (Ridley), collected from the South Sea of China at Zhanjiang, Guangdong. The molecular formula is C28H35O12Cl. The research result by X-ray diffraction method on the crystal structure is presented. The compound is orthorhombic with space group P2(1)2(1)2, cell dimensions a = 16.936, b = 16.709, c = 10.333 A, and Z = 4. The structure has been solved by direct method and refined to R = 0.055 for 2257 unique observable reflexions by least-squares. The molecule is composed of the major conformational isomer in which the three main rings (a six-membered ring, an eight-membered ring, a six-membered ring) take separately the form of chair-chairboat-chair, a five-membered actone ring, a C1 substitution, 4 acetate groups, and a three-membered epoxide ring. The absolute configuration of the molecule has also been determined by statistics (R factor ratio R = 1.012) and Bijvoet pairs observation. For 30 pairs of the greatest anomalous contributions the residuals are R'(+) = 0.057 for the first enantiomorph and R'(-) = 0.005 for the second one, so the latter should unambiguously correspond to the absolute configuration of the molecule.

The growth of single crystal and the determination of crystallographic parameters of (L-tryptophan)A1-insulin and (D-tryptophan)A1-insulin.

The crystal-growing conditions and the results of preliminary X-ray crystallographic analysis of (L-Try)A1-insulin and (D-Try)A1-insulin are reported. The single crystals of this pair of insulin analogue suitable for X-ray diffraction analysis have been grown in the citrate buffer system by still-setting method. They both belong to the trigonal system with space group R3. The parameters of the unit cell (L-Trp)A1-insulin are aH = 80.31A, cH = 37.45A and those of (D-Trp)A1-insulin aH = 79.48A, cH = 43.81A. There are two molecules in an asymmetric unit. The obtained results are discussed.

The growth of single crystals of (L-arginine)B0 bovine insulin and their preliminary X-ray crystallographic analysis.

The crystals of (L-Arg)B0 bovine insulin large enough for X-ray structure analysis have been grown by vapour diffusion in a buffer containing citrate, acetone and zinc chloride. The X-ray diffraction of the crystals extends to 3.0 A spacing. The crystals belong to the trigonal system with unit cell dimension of a = b = 81.82 A, c = 35.05 A, alpha = beta = 90 degrees, gamma = 120 degrees, space group R3. There are two insulin molecules in the crystallographic asymmetric unit.