Sakae Hada

Prediction of retention times in reversed-phase high-performance liquid chromatography from the chemical structure

The capacity factor, k′, on a Zorbax ODS column in methanol-water solvents was determined for alcohols and ethers with positional and geometric isomers by high-performance liquid chromatography. These log k′ values are almost linearly correlated with the molecular cavity surface areas, S, various molecular connectivity indices, e.g., the first-order index, 1χ, the logarithm of the octanol-water partition coefficient, P, and the logarithm of the aqueous solubility. The three parameters S, 1χ and log P are best correlated with log k′. The advantages and disadvantages of these parameters in the correlation with log k′ are considered. The present log k′ data can be used for prediction of log P and log k′ for other compounds including amino acids.

Existence of critical demicellization concentration

Abstract The existence of the critical demicellization concentration (CDC) which had been predicted by Mysels has been demonstrated in the system of mixed fluorocarbon (NF) and hydrocarbon (STrS) surfactants in 0.05 M sodium chloride solution at 30°C. The composition of mixed micelles of NF and STrS was determined from the surface tension data on NF-STrS solutions above the critical micelle concentration (CMC). The region in which the surface tension remains unchanged with the micellar composition was observed. Both ends of this region, xA and xB (xA

Cavity surface areas and solubilities of alkanes in water

Computed cavity surface areas are not directly proportional but linear to cavity areas determined by packing spheres around CPK (Corey-Pauling-Koltun) models. For single-conformation alkanes, log xw (solubility in water in mole fraction units) is not directly proportional but linear to these areas. Group cavity areas are given for estimation of molecular cavity areas.

Quantitative estimation of the bitter taste intensity of oxyphenonium bromide reduced by cyclodextrins from electromotive force measurements.

The bitter taste of oxyphenonium bromide, an antiacetylcholine drug, is suppressed by cyclodextrins. The extent of the suppression can be predicted from the electromotive force measurements with an oxyphenonium bromide-selective electrode. The relationship between the bitter taste intensity and the electromotive force holds true, regardless of the kind and concentration of natural and modified cyclodextrins. This result is explicable on the basis of the observation that both the bitter taste and the electric potential are determined by the concentration of free oxyphenonium bromide. Some implications and limitations of the present approach are discussed.

Spin-state equilibrium in the model complexes of azide hemoprotein

Addition of NaN3 to ferric protohemin biscoordinated with 1-methylimidazole (1-MeIm) or 2-methylimidazole (2-MeIm) in (CH3)2SO resulted in sizeable visible absorption changes, corresponding to the formation of the mixed ligand complexes, hemin X N-3 X 1-MeIm and hemin X N-3 X 2-MeIm. The visible absorption spectrum of the 1-MeIm complex was closely similar to those of azide hemoproteins, while the 2-MeIm derivative exhibited intensified 500 and 625 nm bands and depressed 540 and 570 nm peaks. The iron-bound N-3 of the model complexes exhibited two infrared stretching bands, which were assigned to the high- and low-spin peaks. The intensity of the high-spin infrared peaks increased at higher temperature. From the analyses of the infrared spectral changes, the thermodynamic values of the thermal spin equilibria were determined to be delta H = -3920 cal/mol and delta S = -11.1 e.u. for hemin X N-3 X 1-MeIm and delta H = -2150 cal/mol and delta S = 7.9 e.u. for hemin X N-3 X 2-MeIm. The thermodynamic values of the 1-MeIm complex are similar to the reported values for azide metmyoglobin, suggesting that the contribution from the nonbonded porphyrin-globin contacts to the spin equilibrium is small in azide metmyoglobin. Comparison of the delta H and delta S values among model systems indicates that delta H and delta S compensation similar to that observed in hemoprotein also holds in the models. This may suggest an underlying common denominator for the spin-equilibrium mechanisms in hemins and hemoproteins.

Two alkyl chains of sulfoxides in water; Intramolecular association

Abstract The CMC or solubility of a series of sulfoxides in water was measured by the surface tension method. The thermodynamic parameters of micellization or solution were calculated from these values and discussed in terms of the intramolecular association between two alkyl chains in the monomeric state. The two alkyl chains of some sulfoxides are too long or too similar to form micelles. Sulfoxides, alkylsulfinylalkanols, and sodium alkyl sulfates (different in the position of the sulfate group), which all have two hydrocarbon chains on a molecule, were classified into the three types: IIL, IIS, and IIE. These types, respectively, correspond to molecules in which a variable chain is longer, shorter, and equal compared with the other chain. The logarithm of CMC or solubility showed a linear relationship with the total number of carbon atoms in the hydrocarbon chains and the slope of this straight line was in the order, single chain ≑ IIL > IIE > IIS. This order was explicable on the basis of an increase in the water contact area accompanying the addition of one methylene group, taking into account the intramolecular association. The increment per methylene in the enthalpy of micellization for type IIS was positive, whereas that for other types was negative.

Electrostatic effects on comicellization of fluorocarbon and hydrocarbon surfactants

Abstract The surface tension of mixtures of an ionic fluorocarbon surfactant (NF; C9F17OC6H4SO3Na) with nonionic (DMS; C12H25SOCH3) and ionic (STS; C14H29SO4Na) hydrocarbon surfactants was measured in the presence of sodium chloride at different concentrations. The CMC vs monomeric composition curve for the NF—STS system broke where two micellar phases coexisted. The break became sharper as the concentration of sodium chloride increased. The micellar composition was determined from the surface tension data above the CMC. In the surface tension vs micellar composition curve, the NF—STS system showed a plateau region whereas the NF—DMS system did not show such a region. In mixed micelles, NF and DMS were completely miscible and NF and STS had a limited mutual solubility. The critical solution temperature and the composition at the critical solution temperature depended on the concentration of sodium chloride. These facts show that the electrostatic factor is involved in the miscibility of these fluorocarbon and hydrocarbon surfactants in micelles.

MICELLAR GROWTH OF OCTAETHYLENE GLYCOL DECYL ETHER

The micelle formation of C10E8, a non-ionic surfactant, has been investigated with Sephadex G-10 by frontal gel-filtration chromatography (GFC) at 298 K. From analysis of the concentration dependence of the centroid volume of the GFC pattern by asymptotic theory, the monomer concentration, C1, of C10E8 is determined as a function of total concentration, C. From the relation between C1 and C, the weight-average aggregation number, nw, of C10E8 micelles is estimated as a function of C. The nw value increases rapidly above the critical micelle concentration (c.m.c.) and levels off at higher concentrations. The derivative GFC pattern also suggests the formation of small micelles (probably dimer) at low concentrations below the c.m.c. These results are explicable by the Tanford theory for the formation of spherical micelles and its modified theory. The micelle size distributions are calculated from these theories. Values of c.m.c. calculated on the basis of a few definitions of the c.m.c. are compared with the observed value.

Quantitative Prediction of the Suppression of Drug-Induced Hemolysis by Cyclodextrins from Surface Tension Data

The suppression of hemolysis induced with 0.7 mmol dm-3 chlorpromazine hydrochloride (CPZ) or 15 mmol dm-3 propantheline bromide (PB) by α-, β-, and γ-cyclodextrins (CyDs) is measured as a function of CyD concentration and is correlated with the surface tension of its solution determined at 310 K. The surface tension data allow us to estimate the 1:1 and 2:1 binding constants of CPZ with CyDs as well as the dimerization constant of CPZ. The 2:1 binding constant of CPZ with γ-CyD is larger than the 1:1 binding constant, whereas the converse result is observed for the PB−γ-CyD system. This cooperative binding of CPZ to γ-CyD would be ascribed to a higher tendency of CPZ to form dimer than that of PB. Both the capabilities of CyDs for hemolysis suppression and surface tension elevation are in the order β-CyD > γ-CyD > α-CyD for 0.7 mmol dm-3 CPZ, whereas those capabilities are in the order β-CyD ≈ γ-CyD > α-CyD for 15 mmol dm-3 PB. The bitter taste reduction and surface tension elevation for a 1.5 mmol dm-3 ...

Thermochromism of the azide complexes of ferric hemoproteins

Abstract The thermochromism of ferric azide hemoglobin and myoglobin was examined in a 0–35°C range and the visible spectra of the two spin isomers were separated from the analysis of the thermochromism. (1) The separated low-spin spectra exhibit intensified 540 and 570 nm peaks and a red-shifted Soret band. The high-spin spectra show characteristic 4-banded visible absorption, which is significantly different from the spectrum of 5-coordinate azide hemin, suggesting that the heme iron of azide hemoprotein remains 6-coordinate during the spin-state transition. (2) A larger thermochromism was observed in carp azide methemoglobin bound with inositol hexaphosphate, in contrast with the results reported on human hemoglobin. The difference between the human and carp hemoglobins was consistently explained in terms of an equilibrium coexistence of the R and T conformers in human azide methemoglobin bound with inositol hexaphosphate.