Self-talk in a basketball-shooting task.

This study examined the effectiveness of two different types of self-talk on the performance of a basketball-shooting task. 60 physical education and sports sciences students were organized into one control and two treatment groups which used self-talk. During the experiment, the control group performed with the general instructions, whereas the self-talk groups used the cue-words "relax" and "fast," respectively, Analysis showed that only the participants of the self-talk group who used the word "relax" improved their performance significantly as compared to the other two groups. It appears that self-talk can positively affect performance if its content is appropriate for the task performed.

Accessibility of tyrosine Y(.)(Z) to exogenous reductants and Mn(2+) in various Photosystem II preparations.

The reduction of tyrosine Y(.)(Z) by benzidine and exogenous Mn(2+) was studied by kinetic EPR experiments in various Photosystem II (PSII) preparations. Using lanthanide treated PSII membranes it was demonstrated that neither the extrinsic polypeptides (17, 23 and 33 kDa) nor the Mn complex block the accessibility of Y(.)(Z) to exogenous reductants, such as benzidine. In addition, it was shown that in the presence of the native Mn complex exogenous Mn(2+) does not reduce Y(.)(Z).

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol.

During the four-stepped catalytic cycle of water oxidation by photosystem II (PSII) molecular oxygen is released in only one of the four reaction steps whereas the release of four protons is distributed over all steps. In principle, the pattern of proton production could be taken as indicative of the partial reactions with bound water. In thylakoids the extent and rate of proton release varies as function of the redox transition and of the pH without concomitant variations of the redox pattern. The variation has allowed to discriminate between deprotonation events of peripheral amino acids (Bohr effects) as opposed to the chemical deprotonation of a particular redox cofactor, and of water. In contrast, in thylakoids grown under intermittent light, as well as in PSII core particles the pattern of proton release is flat and independent of the pH. This has been attributed to the lack in these materials of the chlorophyll a,b-binding (CAB) proteins. We now found that a thylakoid-like, oscillatory pattern of proton release was restored simply by the addition of glycerol which modifies the protein-protein interaction. Being a further proof for the electrostatic origin of the greater portion of proton release, this effect will serve as an important tool in further studies of water oxidation.

Proton NMR comparison of noncovalent and covalently cross-linked complexes of cytochrome c peroxidase with horse, tuna, and yeast ferricytochromes c.

Proton NMR spectroscopy at 500 and 361 MHz has been used to characterize the noncovalent or electrostatic complexes of yeast cytochrome c peroxidase (CcP) with horse, tuna, yeast isozyme-1, and yeast isozyme-2 ferricytochromes c and the covalently cross-linked complexes of cytochrome c peroxidase with horse and yeast isozyme-1 ferricytochromes c. Under the conditions employed in this work, the stoichiometry of the predominant complex formed in solution (which totaled greater than 90% of complex formed) was found to be 1:1 in all cases. These studies have elucidated significant differences in the proton NMR absorption spectra and the one-dimensional nuclear Overhauser effect difference spectra of the complexes, depending on the specific species of ferricytochrome c incorporated. In particular, the results indicate that the noncovalent complexes formed between CcP and physiological redox partners (yeast isozyme-1 or yeast isozyme-2 ferricytochromes c) are distinctly different from the noncovalent complexes formed between CcP and ferricytochromes c from horse and tuna. Parallel chemical cross-linking studies carried out using mixtures of cytochrome c peroxidase with horse ferricytochrome c, and cytochrome c peroxidase with yeast isozyme-1 ferricytochrome c further emphasize such cytochrome c-dependent differences, with only the covalently cross-linked complex of physiological redox partners (cytochrome c peroxidase/yeast isozyme-1) displaying NMR spectra characteristic of a heterogeneous mixture of different 1:1 complexes. Finally, one-dimensional nuclear Overhauser effect experiments have proven valuable in selectively and efficiently probing the protein-protein interface in these complexes, including the environment around the cytochrome c heme 3-methyl group and Phe-82.