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- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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| 5. |
- Zhang, L. N., et al.
(författare)
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Solution properties of antitumor sulfated derivative of alpha-(1 -> 3)-D-glucan from Ganoderma lucidum
- 2000
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Ingår i: Bioscience, biotechnology and biochemistry. - : Oxford University Press (OUP). - 0916-8451 .- 1347-6947. ; 64:10, s. 2172-2178
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Tidskriftsartikel (refereegranskat)abstract
- Four fractions of a water-insoluble alpha-(1-->3)-D-glucan GL extracted from fruiting bodies of Ganoderma lucidum were dissolved in 0.25 M LiCl/DMsO, and then reacted with sulfur trioxide-pyridine complex at 80 degreesC to synthesize a series of water-soluble sulfated derivatives S-GL. The degree of substitution of DS was measured by using IR infrared spectra, elemental analysis, and C-13 NMR to be 1.2-1.6 in the non-selective sulfation. Weight-average molecular weight M, and intrinsic viscosity [eta] of the sulfated derivatives S-GL were measured by multi-angle laser light scattering and viscometry. The M-w value (2.4 x 10(4)) of sulfated glucan S-GL-1 was much lower than that (44.5 x 10(4)) of original alpha-(1-->3)-D-glucan GL-1. The Mark-Houwink equation and average value of characteristic ratio C-infinity for the S-GL in 0.2 M NaCl aqueous solution at 25 degreesC were found to be: [eta] =1.32 x 10(-3) M-w(1.06) (cm(3) g(-1)) and 16, respectively, in the M-w range from 1.1 x 10(4) to 2.4 x 10(4). It indicated that the sulfated derivatives of the alpha-(1-->3)-D-glucan in the aqueous solution behave as an expanded chain, owing to intramolecular hydrogen bonding or interaction between charge groups. Interestingly, two sulfated derivatives synthesized from the alpha-(1-->3)-D-glucan and curdlan, a beta-(1-->3)-D-glucan, all had significant higher antitumor activity against Ehrlich ascites carcinoma (EAC) than the originals. The effect of expanded chains of the sulfated glucan in the aqueous solution on the improvement of the antitumor activity could not be negligible.
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| 6. |
- Zhang, L., et al.
(författare)
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Transition from triple helix to coil of Lentinan in solution measured by SEC, viscometry, and C-13 NMR
- 2002
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Ingår i: Polymer journal. - : Springer Science and Business Media LLC. - 0032-3896 .- 1349-0540. ; 34:6, s. 443-449
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Tidskriftsartikel (refereegranskat)abstract
- Lentinan, beta-(1 --> 3)-D-glucan with (1 --> 6) branching, was isolated from Lentinus edodes. Weight-average molecular weight M-w radius of gyration < s(2) > (1/2) and intrinsic viscosity [eta] of Lentinan in 0.2 M NaCl aqueous solution, dimethylsulfoxide (DMSO) and water/DMSO mixtures were measured by light scattering (LS), size exclusion chromatography (SEC) combined with LS, and viscometry. The results indicated that the glucan exists mainly as triple-helical chains in 0.2 M NaCl aqueous solution and water/DMSO mixtures with over 20 wt% water content, and as single-flexible chain in DMSO. The data from SEC-LS, viscosity and C-13 NMR measurements proved strongly that the helix-coil conformation transition occurred in a narrow range from 80 to 85 wt% DMSO aqueous solution, accompanying with obvious changes of M-w, < s(2) >(1/2)(z), [eta] as well as signals of C6 and C6(s). The transition of Lentinan in water/DMSO mixture was irreversible. The difference in C-13 NMR spectra for the triple-helical and coil conformations was the disappearance of the signals of C3 in beta-(1 --> 3)- linked backbone and the enhancement in relative intensities of glucose substituted C6s in the helix state, as well as the appearance of an asymmetric and broad peak of C6 in the intermediate of the conformation change. This suggests that the immobilization of the backbone by binding with intra and intermolecular hydrogen bonds resulted in the loss of the signals of its carbon atoms in the triple helix state. An overcoating cylinder model composed of the beta-(1 --> 3)- linked backbone as helix core and the side chains as rotatable overcoat was proposed to illustrate the triple-helical conformation and its transition in the solution.
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