PubMed · 7403250
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M Dittgen, H Kala, H Moldenhauer, G Zessin, J Schneider. 1980. [Pharmaceutical granulation technology].. https://pubmed.ncbi.nlm.nih.gov/7403250/
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A 1000 base pair (bp) model supercoiled DNA is simulated using spherical screened Coulomb interactions between subunits on one hand and equivalent hard-cylinder interactions on the other. The amplitudes, or effective charges, of the spherical screened Coulomb electrostatic potentials are chosen so that the electrostatic potential surrounding the middle of a linear array of 2001 subunits (31.8 A diameter) closely matches the solution of the nonlinear Poisson-Boltzmann equation for a cylinder with 12 A radius and the full linear charge density of DNA at all distances beyond the 24 A hard-core diameter. This superposition of spherical screened Coulomb potentials is practically identical to the particular solution of the cylindrical linearized Poisson-Boltzmann equation that matches the solution of the nonlinear Poisson-Boltzmann equation at large distances. The interaction energy between subunits is reckoned from the effective charges according to the standard DLVO expression. The equivalent hard-cylinder diameter is chosen following Stigter's protocol for matching second virial coefficients, but for the full linear charge density of DNA. The electrostatic persistence length of the model with screened Coulomb interactions is extremely sensitive to the (arbitrarily) chosen subunit length at the higher salt concentrations. The persistence length of the hard-cylinder model is adjusted to match that of the screened Coulomb model for each ionic condition. Simulations for a superhelix density sigma = -0.05 using a spherical screened Coulomb interaction plus a 24 A hard-cylinder core (SCPHC) potential indicate that the radius of gyration of this 1000 bp DNA actually undergoes a slight increase as the NaCl concentration is raised from 0.01 to 1.0M. Thus, merely softening the potential from hard-cylinder to screened Coulomb form does not produce a large decrease in radius of gyration with increasing NaCl concentration for DNAs of this size. Radii of gyration, static structure factors, and diffusion coefficients obtained using the equivalent hard-cylinder (EHC) potential agree well with those obtained using the SCPHC potential in 1.0M NaCl, but in 0.1M NaCl the agreement is not as good, and in 0.01M NaCl the agreement is definitely unsatisfactory. These conclusions differ in significant respects from those obtained in previous studies.
The infrared spectrum of hot water observed in a sunspot has been assigned. The high temperature of the sunspot (3200 K) gave rise to a highly congested pure rotational spectrum in the 10-micrometer region that involved energy levels at least halfway to dissociation. Traditional spectroscopy, based on perturbation theory, is inadequate for this problem. Instead, accurate variational solutions of the vibration-rotation Schrödinger equation were used to make assignments, revealing unexpected features, including rotational difference bands and fewer degeneracies than anticipated. These results indicate that a shift away from perturbation theory to first principles calculations is necessary in order to assign spectra of hot polyatomic molecules such as water.
The influences of the pore size of base silica gels and the bound amounts of ovoglycoprotein (OGCHI) on the chiral resolution of racemates have been investigated. To the 12-, 20- and 30-nm pore size silica gels, aminopropyl groups were introduced, activated with N,N'-disuccinimidyl carbonate and then reacted with OGCHI followed by blocking with D-glucosamine. For the OGCHI material prepared with the same pore size silica gel, a linear correlation was obtained between the capacity factor or each enantiomer and the amount of bound OGCHI. Enantioselectivity and resolution obtained with the reaction of 40 mg OGCHI per 1 g silica gel were lower than those obtained with the reaction of 80, 160 and 320 mg OGCHI, when the same pore size silica gel was used. This is due to the superfluous achiral interaction with base silica gels and/or spacers because of low protein coverage. With regard to comparison of the pore sizes of silica gel, the OGCHI materials prepared with the 12-nm pore size silica gel gave the largest capacity factor, and the highest enantioselectivity and/or resolution for the racemates tested, when the same amount of OGCHI was reacted. Thus, the OGCHI materials were prepared with the reaction of 80 mg OGCHI per 1 g silica gel having a 12-nm pore size followed by blocking with D-glucosamine. By diminishing the superfluous achiral interaction with base silica materials and/or spacers, much more efficient OGCHI materials should be obtainable.