Bacillus Calmette-Guérin (BCG) vaccine, developed originally for the prophylaxis of tuberculosis, is a potent immunostimulant used to treat superficial bladder carcinoma in man. The aim of this study was to compare the molecular weight and self-association properties of an antineoplastic glucan (PS1A1) extracted from BCG vaccine as determined by different techniques including diffusion, light-scattering and chromatographic methods. In the diffusion experiments, a semi-empirical relationship was derived between the effective diffusion coefficients, Dp, and the weight-average molecular weights, Mw, of several dextrans used as standards, according to the equation Dp = 2.233 x 10(-6) x Mw(-0.66). On the basis of this relationship, the molecular weight of PS1A1 was found to be 57.4 kDa, although, unexpectedly, membrane association was high, most probably because of molecular branching. In the light-scattering experiment it was observed that, unlike dextran, PS1A1 undergoes concentration-dependent multimerization in water. However, the molecular weight of PS1A1 in 0.1 M sodium chloride ranged from 60 to 68 kDa, with a mean of 65 kDa, over the same concentration range. This value was in agreement with the molecular weight determined for PS1A1 by gel-filtration chromatography in previous studies, suggesting that 65 kDa represents the approximate monomeric size of the unassociated molecule. Thus, it was evident that the aggregation was suppressed by electrolyte. Elemental analysis by X-ray fluorescence showed that PS1A1 contained carbon, oxygen, hydrogen and phosphorus, indicating that hitherto unobserved ionized phosphate groups might promote electrostatic interactions.
The chemical and spectroscopic properties of several reaction products of 17β‐hydroxy‐1,3‐seco‐2‐nor‐5α‐estran‐1‐oic acid and 17β‐hydroxy‐1,3‐seco‐2‐nor‐4‐oxo‐5α‐estran‐1‐oic acid were examined and found to be atypical. For instance, the methyl ester of the first acid was resistant to basic hydrolysis conditions but partly hydrolyzed with 100% H2SO4. Reduction of the ester by LiA1H4 gave 1,3‐seco‐2‐nor‐5α‐estrane‐1,17β‐diol from which diacetate, ditosylate and 17‐monotosylate derivatives were prepared. The C‐1 methylene protons of each appeared as a singlet in 60, 100 and/or 270 MHz NMR spectra. The methyl ester and the diacetate of the diol were synthesized by alternate methods to verify the assigned structures. A 470‐MHz spectrum eventually resolved the C‐1 methylene protons of the monotysylate into the AB portion of an ABX pattern, further confirming the assigned structures. Also, 2,3‐seco‐1‐oxo‐5α‐estran‐17β‐ol 17‐nitrate was synthesized.
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