Electrostatic attraction between cationic-anionic assemblies with surface compositional heterogeneities

Electrostatics plays a key role in biomolecular assembly. Oppositely charged biomolecules, for instance, can co-assembled into functional units, such as DNA and histone proteins into nucleosomes and actin-binding protein complexes into cytoskeleton components, at appropriate ionic conditions. These cationic-anionic co-assemblies often have surface charge heterogeneities that result from the delicate balance between electrostatics and packing constraints. Despite their importance, the precise role of surface charge heterogeneities in the organization of cationic-anionic co-assemblies is not well understood. We show here that co-assemblies with charge heterogeneities strongly interact through polarization of the domains. We find that this leads to symmetry breaking, which is important for functional capabilities, and structural changes, which is crucial in the organization of co-assemblies. We determine the range and strength of the attraction as a function of the competition between the steric and hydrophobic constraints and electrostatic interactions.Comment: JCP June/200

Unusual features in the nonlinear microwave surface impedance of Y-Ba-Cu-O thin films

Striking features have been found in the nonlinear microwave (8 GHz) surface impedance $Z_s=R_s + jX_s$ of high-quality YBaCuO thin films with comparable low power characteristics [$R_{res}\sim 35--60 \mu\Omega$ and $\lambda_L(15 K)\sim 130--260 nm$]. The surface resistance $R_s$ is found to increase, decrease, or remain independent of the microwave field $H_{rf}$ (up to 60 mT) at different temperatures and for different samples. However, the surface reactance $X_s$ always follows the same functional form. Mechanisms which may be responsible for the observed variations in $R_s$ and $X_s$ are briefly discussed.Comment: 4 pages, 4 figure

Leukocytes phagocytic activity under moderate hypotension conditions in some representatives of bony fish, amphibians and reptiles

The leukocytes phagocytic activity against Bacillus subtilis and agromerulated latex particles in representatives of bony fish, amphibians and reptiles under reduced medium osmolarity conditions was studied. It was found that in moderate hypotension compared with isotonia, the white blood cells absorption capacity of the fish was not changed, but it was reduced for amphibians and reptile

On the determination of the quasiparticle scattering rate in unconventional superconductors by microwave surface impedance

In the approximation of validity of the Drude expression for quasiparticle conductivity and the assumption that all electrons at T = 0 transform into a superfluide condensate, the expression for the quasiparticle scattering rate tau -1 in terms of the real and imaginary parts of the microwave surface impedance has been obtained. The resulting expression is a generalization of the well-known expression for tau^-1, valid for omega x tau is much less 1, to an arbitrary value of omega x tau, where omega is the frequency of the microwave field. From experimental Ka-band impedance measurements, temperature dependence of tau^-1 in superconducting single crystal pnictides Ba(Fe1-xCox)2As2 is obtained using the generalized expression. It is shown that under condition of the given work, the approximation omega x tau is much less 1 gives the considerable error in determination of tau^-1.Comment: 3 pages, 1 figur

Изучение влияния наночастиц серебра in vitro на уровень экспрессии молекулярных маркеров активации лимфоцитов и маркера аутоиммунного процесса периферической крови больных вирусной патологией роговицы

Изучено влияние in vitro наночастиц серебра на экспрессию молекулярных маркеров активации лимфоидных клеток СD 7+, CD 25+, CD 38+, CD 45+, CD 54+, CD 95+, CD 150+ и маркера аутоиммунного процесса CD 5+, а также на фагоцитарную активность нейтрофилов у больных с вирусной патологией роговицы. В лаборатории иммунологии ГУ «Институт глазных болезней и тканевой терапии им. В.П. Филатова НАМН Украины» была разработана методика культивирования лимфоцитов периферической крови с иммуномодулирующими препаратами, с последующим определением изменения уровня экспрессии молекулярных маркеров активации лимфоцитов. Оценка уровня экспрессии молекулярных маркеров активации лимфоцитов периферической крови проводилась гистоиммуноцитохимическим методом, с использованием панели моноклональных антител CD 5+, СD 7+, CD 25+, CD 38+, CD 45+, CD 54+, CD 95+ и CD 150+. Исследование было проведено in vitro с лимфоцитами периферической крови 23 больных вирусной патологией роговой оболочки глаза. Проведенные нами исследования по изучению воздействия in vitro частиц наносеребра на состояние экспрессии молекулярных маркеров активации лимфоцитов периферической крови и фагоцитарную активность нейтрофилов у больных с вирусной патологией роговицы, показали достоверное повышение уровня экспрессии СD7+, CD 25+, CD 45+ и фагоцитарной активности нейтрофилов после применения наночастиц серебра

Impact ionization and large room-temperature magnetoresistance in micron-sized high-mobility InAs channels

We report on hot electron induced impact ionization and large room-temperature magnetoresistance (MR) in micron-sized channels of n-type high-mobility InAs (μ=3.3m2V−1s−1 at T=300K): the MR reaches values of up to 450% in magnetic fields of 1 T and applied voltages of ∼1 V and is weakly dependent on temperature. We present Monte Carlo simulations of the hot electron dynamics to account for the large MR and its dependence on the sample geometry and applied electric and magnetic fields. Our work demonstrates that the impact ionization of electrons at room temperature, under small applied magnetic fields (<1 T) and small voltages (<1 V), can provide an extremely sensitive mechanism for controlling the electrical resistance of high-mobility semiconductors