The proton acceptor group in the recently described retinal protein, proteorhodopsin has an unusually high pK(a) of 7.1. It was shown that at pH above this pK(a), illumination initiates a photocycle similar to that of bacteriorhodopsin, and the protein transports proton across the cell membrane. Recently it was reported that proteorhodopsin, unlike bacteriorhodopsin, transports protons at pH below the pK(a) of the proton acceptor, and this transport is in the reverse direction. We have investigated the photocycle of proteorhodopsin at such low pH. At pH 5, three spectrally distinct intermediates K, L, and N, and another spectrally silent one, PR', could be identified, but a deprotonated Schiff base containing M-like intermediate, characteristic for proton pumping activity, does not accumulate. All the reactions between the intermediates are close to equilibrium, except the last transition from PR' to PR, when the protein returns to its initial unexcited state in a quasiunidirectional reaction. The electric signal measurements indicate that although charge motions are detected inside the protein, their net dislocation is zero, indicating that contrary to the earlier reported, at low pH no charged particle is transported across the membrane.
The circulatory apparatus has as a main function the constant maintaining of the internal environment in all the regions of the organism. The blood is a liquid tissue, being formed of a fundamental substance – plasma and blood cells. Heart is the central organ of the cardiovascular apparatus. The heart muscles have numerous biophysical properties. The cardiac muscle is never tired unless it suffered a pathological process. During the diastole, blood is aspired in the heart and during the systole it is pushed in the big and small circulation. The blood amount pushed from the heart in the vascular system in a certain time represents the blood flow. The biophysical methods are next: we administer a certain substance amount, then its passing speed will depend on its concentration; to apply the calorimetric principles for the measurement of the gastric blood flow; the diagnostic of a chronic peripheral arteriopathy we use the calorimetric method is based on measuring the heat being introduced in a certain amount of water which has known temperature; one of the most often used methods for the evaluation of the use of radioisotopes in the cardio-vascular system is the compartment method. Any attempt to apply biophysics to the life systems involves three stages. First we observe the phenomena and formulate a biophysical description in the form of equations; after to solve the equations. Finally we return to the real life system and interpret this solution in terms of reality, this interpretation may requiew experimental testing.
Low back pain (LBP) is a disease with a high socio-economic and medical impact. Recovery treatment is complex and includes medication (NSAIDs, analgesics, muscle relaxants), physiotherapy and kinesiology. Ultrasound is one of the electrotherapy procedures applied due to its analgesic effects, muscle relaxing properties and massage. The study assesses the evolution of temperature and the number of red blood cells after the application of ultrasound of different intensities and ways. The results are statistically significant for some parameters. Limitations of the study are determined by the relatively small number of study patients, but the results could form the basis of further research.
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