A.E. De Vries

Interaction of basic polyamino acids with the red blood cell I. combination of polylysine with single cells

Abstract 1. 1. The interaction between negatively charged cells and positively charged (basic) polyelectrolytes is mainly due to non-specific electrostatic attractive forces. 2. 2. Adsorption of polylysine (PL) on the red blood cell is a reversible reaction which rapidly attains a state of equilibrium; consequently the surface potential of the erythrocyte in PL solutions is a single-valued function of the equilibrium concentration of free PL in solution. 3. 3. A method is described whereby mobility data can be used to evaluate both the concentration of PL in solution and the amount adsorbed on the cells. 4. 4. An adsorption isotherm of the Freundlich type was obtained which is characteristic of the interaction of PL with the red blood cell at pH 7.2 and ionic strength 0.15. 5. 5. With red blood cells, PL is bound by the membrane only. 6. 6. PL adsorption on the surface of glass particles and their electrophoretic mobilities were measured. 7. 7. The orientation, and the hemolytic effect, of PL molecules adsorbed on the red cell membrane are discussed.

Rotational relaxation numbers for the isotopic molecules of N2 and Co

In order to establish the influence of forbidden transitions, rotational relaxation numbers Zrot of the gases 14N2, 14N15N, 15N2, 12C16O and 12C18O were determined from ultrasonic absorption measurements. The absorption coefficient was measured in a single-crystal interferometer at a frequency of 3.007 MHz and a temperature of 307.46 K in the pressure range from 75–200 torr. The ratio of the experimental and the classical absorption coefficients determines Zrot. The following results were obtained: Zrot(14N2) = 3.9,Zrot(14N15N) = 4.1 Zrot(15N2) = 4.5, Zrot(12C16O) = 2.8 and Zrot(12C18O) = 2.7. No influence on the Z value due to the symmetry of the homonuclear N2 molecules is observed. A short discussion is given.

The influence of the distribution of atomic masses within the molecule on thermal diffusion: I. Isotopic CO and N2 molecules

Abstract Separations by thermal diffusion in different isotopic mixtures of CO and N 2 were studied in a “Trennschaukel” between 80°K and 303°K. The observed separations were strongly influenced by the distribution of the atomic masses within the molecule. For the mixtures 12 C 18 O/ 12 C 16 O, 14 C 16 O/ 12 C 16 O and 12 C 18 O/ 14 C 16 O the thermal diffusion factor becomes zero at 110°K, 175°K and 250°K respectively. These differences cause very big differences in experimentally established potential parameters. The separations are very well described by the dimensional treatment of Waldmann which gives the thermal diffusion factor as a sum of a translational and a rotational part. From the observed separations the dependence of the diffusionconstant on temperature was calculated. Within the usual experimental accuracy no difference is found between the different isotopic molecules.

The influence of the distribution of atomic masses within the molecule on thermal diffusion: II. Isotopic methane and methane/argon mixtures

Abstract The temperature dependence of the thermal diffusion factor for several isotopic mixtures of methane and mixtures of argon and methane was studied in two swing separators between 80δK and 300δK. The isotopic mixtures showed a noticeable influence of the mass-distribution within the molecule, whereas a description with a Lennard-Jones (12,6) potential remained still possible. These mixtures could be classified roughly into two categories, one with a potential well depth of 190–196δK, the other with one of 223–225δK. The first consisted of mixtures of spherical top molecules with zero difference in the moments of inertia, the second of mixtures of molecules with different moments of inertia. From the comparison between theoretical and experimental results it is concluded that viscosity is not seriously affected by the presence of inelastic collisions, while diffusion and thermal diffusion would give smaller and larger ϵ-values, respectively, if described by the Chapman-Enskog theory. For all studied mixtures of methane and argon the inversion temperature was found to be 137.5°K. A concentration reversion in these mixtures gave an unexpected small change of the thermal diffusion factor. Inelastic collision between argon and methane are probably much less important than those between two methane molecules.

Rotational relaxation in mixtures of methane with helium, argon and xenon

Abstract Measurements of ultrasonic absorption have been made in binary mixtures of methane with the noble gases helium, argon and xenon. The absorption coefficients were measured in a single-crystal interferometer at a frequency of 3.001 MHz and a temperature of 308.3 K in the pressure range from 100 to 150 torr. Rotational relaxation times and numbers were derived from the observed absorption. The estimated collision numbers for translational-rotational energy exchange are: Zrot (CH4−CH4) = 12.3, Zrot (CH4−He) = 3, Zrot (CH4−Ar) = 12, Zrot (CH4−Xe) = 27. Calculations of rotational relaxation numbers Zrot of spherical top molecules in an inert gas have been made by Widom and Sather and Dahler. Although their values are higher, they predict the same tendency as we found experimentally.

Measurement of vibrational relaxation times in the spectrophone by the amplitude-frequency response method

Abstract The amplitude-frequency response method of the optic-acoustic effect has been used to study vibrational-vibrational and vibrational-translational relaxation times in CO2 and mixtures of CO2 with He, Ar and Kr. The results show that relaxation of the asymmetric stretching vibration of CO2 towards translation occurs via a two-step relaxation process. Evidence has been found that the first step is the transition from the (0, 0, 1) state of CO2 to the (0, 2, 0) or the (1, 0, 0) state. The second step is the degradation of the bending vibrational energy to translational energy.

The potential model for helium-hydrogen interaction in thermal diffusion

Abstract The thermal diffusion factors α of small concentrations of all possible hydrogen isotopes were measured in 3 He and 4 He between 100°C and 500°C and compared with the values from the Chapman-Enskog theory. It appeared that a Buckingham exp. 6 potential model with parameters from viscosity and second virial coefficients, could fit the separations of the symmetric molecules H 2 , D 2 and T 2 . It was, however, impossible to fit the values of the asymmetric molecules HD, HT and DT into the Chapman-Enskog theory. An analysis of possible sources of deviations, such as higher order approximations, quantum corrections or inelastic collisions, gave no improvement of the theoretical values. The effect has to be found in the angular dependence of the intermolecular potential, originated by the shift of the centre of mass of the molecule, which is, however, out of the scope of a spherically symmetric theory. The situation is in complete agreement with the mutual thermal diffusion of hydrogen isotopes 2 ). Both series of experiments could be described by the following approximate formula

Ultraviolet‐Induced Isotope Exchanges in Gaseous Mixtures of HCl and D2 and of DCl and H2

Mixtures of HCl and D2 and of DCl and H2 were irradiated with an ultraviolet mercury resonance lamp and analyzed mass spectrometrically for the different isotopic species of hydrogen. It was found that at room temperature the reaction H+DCl→HD+Cl is slower than the exchange reaction H+DCl→D+HCl. This is to be expected from a consideration of activation energies, but it is in apparent contradiction to earlier results obtained by Leighton and Cross and by Steiner and Rideal. The reaction between hydrogen atoms and hydrogen molecules was found to be much faster at this temperature than is usually estimated.

Thermal diffusion in ternary mixtures: II. Experiments

Synopsis Experimental results on thermal diffusion in mixtures of two isotopes with one non-isotopic component are compared with the theory developed in paper I10). Some experimental results are; α(22Ne−20Ne) in pure neon is 0.027 at 490°K, in mixtures with 100% H2: 0.009, in mixtures with 100% He: 0.013; α(4He−3He)(10% 3He) in pure helium is 0.060 at 490°K, in mixtures with 100% Ne: 0.011; α(40Ar−36Ar) in pure argon is 0.014 at 440°K, in mixtures with 100% Ne: 0.034; α(14CO−12CO) in pure carbonmonoxide is 0.020 at 410°K, in mixtures with 100% C2H4: 0.014; in mixtures with 100% C2H2D2: 0.014; in mixtures with 100% C2H6: 0.011. In general the agreement between theory and experiment is satisfactory.

Rotational relaxation numbers from thermal transpiration measurements

Abstract Rotational relaxation numbers Zrot of the gases N2, O2, CO, CO2 and CH4 were determined at a mean temperature of 500°K by means of thermal transpiration measurements. Special attention was given to possible differences in Zrot-values of isotopic molecules: CH4 and CD4, 14N15N and 14N2, 12C16O and 12C18O. The following results were obtained: Zrot(N2) = 3.8, Zrot(CO2) = 3.9, Zrot(CO) = 1.9, Zrot(O2) = = 4.2 and Zrot(CH4) = 14.8. No differences in Zrot-values were found between the different isotopic molecules in the case of nitrogen and carbonmonoxide, whereas Zrot(CD4) was about half the value obtained for CH4, in agreement with acoustical results.