Protein dynamics control of electron transfer in photosynthetic reaction centers from Rps. sulfoviridis.

In the cycle of photosynthetic reaction centers, the initially oxidized special pair of bacteriochlorophyll molecules is subsequently reduced by an electron transferred over a chain of four hemes of the complex. Here, we examine the kinetics of electron transfer between the proximal heme c-559 of the chain and the oxidized special pair in the reaction center from Rps. sulfoviridis in the range of temperatures from 294 to 40 K. The experimental data were obtained for three redox states of the reaction center, in which one, two, or three nearest hemes of the chain are reduced prior to special pair oxidation. The experimental kinetic data are analyzed in terms of a Sumi-Marcus-type model developed in our previous paper,1 in which similar measurements were reported on the reaction centers from Rps. viridis. The model allows us to establish a connection between the observed nonexponential electron-transfer kinetics and the local structural relaxation dynamics of the reaction center protein on the microsecond time scale. The activation energy for relaxation dynamics of the protein medium has been found to be around 0.1 eV for all three redox states, which is in contrast to a value around 0.4-0.6 eV in Rps. viridis.1 The possible nature of the difference between the reaction centers from Rps. viridis and Rps. sulfoviridis, which are believed to be very similar, is discussed. The role of the protein glass transition at low temperatures and that of internal water molecules in the process are analyzed.

[Use of octagam and pentaglobin in the treatment of severe sepsis in the neonatal period]. / Primenenie oktagama i pentaglobina v lechenii tiazhelogo sepsisa v neonatal'nom periode.

Many patients with sepsis are immunocompetent. They respond well to standard combinations of antibiotics and cardiovascular support. However, immunocompetent patients, particularly small-for-date newborns, are in need of stronger immune protection. Although the mechanisms due to which antibody preparations yield positive effects are not quite clear, clinical studies carried out in many countries and our own results indicate a high protective effect of intravenous immunoglobulins and necessitate their use at least in intensive care departments.

[Changes in the beta 2-microglobulin level during hemodialysis]. / Izmenenie urovnia beta 2-mikroglobulina vo vremia gemodializa.

The authors studied changes of the beta 2-microglobulin level during hemodialysis with dialyzers AIP-02-02 (cuprophane membrane), E2 (cuprophane membrane), AIP-03-02 (polysulfone membrane), F60 (polysulfone membrane), and hemodiafiltration with dialyzer F60. The following data were obtained. The beta 2-microglobulin level in patients undergoing hemodialysis is approximately 20 times the normal level. No essential fluctuations of the level of this protein occurs during hemodialysis and hemodiafiltration. The cuprophane membrane does not cause increase of beta 2-microglobulin generation during hemodialysis. Standard hemodialysis with the cuprophane membrane and the highly-permeable polysulfone membrane does not lead to decrease of the beta 2-microglobulin level. Hemodiafiltration with the highly-permeable polysulfone membrane is an effective method for the elimination of this protein.