Dynamics of tRNA at different levels of hydration.

The influence of hydration on the nanosecond timescale dynamics of tRNA is investigated using neutron scattering spectroscopy. Unlike protein dynamics, the dynamics of tRNA is not affected by methyl group rotation. This allows for a simpler analysis of the influence of hydration on the conformational motions in RNA. We find that hydration affects the dynamics of tRNA significantly more than that of lysozyme. Both the characteristic length scale and the timescale of the conformational motions in tRNA depend strongly on hydration. Even the characteristic temperature of the so-called "dynamical transition" appears to be hydration-dependent in tRNA. The amplitude of the conformational motions in fully hydrated tRNA is almost twice as large as in hydrated lysozyme. We ascribe these differences to a more open and flexible structure of hydrated RNA, and to a larger fraction and different nature of hydrophilic sites. The latter leads to a higher density of water that makes the biomolecule more flexible. All-atom molecular-dynamics simulations are used to show that the extent of hydration is greater in tRNA than in lysozyme. We propose that water acts as a "lubricant" in facilitating enhanced motion in solvated RNA molecules.

Schizophrenia and polymorphic CAG repeats array of calcium-activated potassium channel (KCNN3) gene in Serbian population.

KCNN3 might be a candidate gene for schizophrenia. The KCNN3 cDNA sequence contains two stretches of CAG trinucleotide repeats encoding two separate polyglutamine segments near the N-terminus of this channel protein. The second CAG repeat is highly polymorphic in the Caucasian population from both Europe and United States. The authors carried out a study to compare the allelic frequency distribution of the CAG repeat in KCNN3 gene in 55 Serbian schizophrenic patients and 46 controls. The data indicate a significant association between longer CAG repeats in second polymorphic KCNN3 region and schizophrenia in the Serbian population.

Excitation transfer in the peridinin-chlorophyll-protein of Amphidinium carterae.

Peridinin-chlorophyll-protein (PCP) is a unique light-harvesting protein that uses carotenoids as its primary light-absorbers. This paper theoretically investigates excitation transfer between carotenoids and chlorophylls in PCP of the dinoflagellate Amphidinium carterae. Calculations based on a description of the electronic states of the participating chromophores and on the atomic level structure of PCP seek to identify the mechanism and pathways of singlet excitation flow. After light absorption the optically allowed states of peridinins share their electronic excitation in excitonic fashion, but are not coupled strongly to chlorophyll residues in PCP. Instead, a gateway to chlorophyll Q(y) excitations is furnished through a low-lying optically forbidden excited state, populated through internal conversion. Carbonyl group and non-hydrogen side groups of peridinin are instrumental in achieving the respective coupling to chlorophyll. Triplet excitation transfer to peridinins, mediated by electron exchange, is found to efficiently protect chlorophylls against photo-oxidation.

Efficient light harvesting through carotenoids.

We review the factors that control the efficiency of carotenoid-chlorophyll excitation transfer in photosynthetic light harvesting. For this we summarize first the recently developed theory that describes electronic couplings between carotenoids and chlorophylls and we outline in particular the influence of length of conjugated system and of symmetry breaking on the couplings. We focus hereby on the structurally solved lycopene-BChl system of LH 2 from Rhodospirillum molischianum and the peridinin-Chl a system of PCP from Amphidinium carterae. In addition, we review recent spectroscopic data for neurosporene, spheroidene and lycopene, three carotenoids with different lengths of conjugated systems. On the basis of the measured energies, emission lineshapes, solution and protein environment lifetimes for their 2A ( g ) (-) and 1B ( u ) (+) states as well as of the theoretically determined couplings, we conclude that the transfer efficiencies from the 2A ( g ) (-) state are controlled by the Car(2A ( g ) (-) )-BChl(Q(g)) electronic couplings and the 2A ( g ) (-) --> 1A ( g ) (-) internal conversion rates. We suggest that symmetry breaking and geometry rather than length of conjugated system dominate couplings involving the 2A ( g ) (-) state. Differences in transfer efficiencies from the 1B ( u ) (+) state in LH 2 and PCP are found to be dominated by the differences in spectral overlap. The role of the 1B ( u ) (+) state is likely to be influenced by a lower-lying (in longer polyenes), optically forbidden 1B ( u ) (-) state.

Architecture and mechanism of the light-harvesting apparatus of purple bacteria.

Photosynthetic organisms fuel their metabolism with light energy and have developed for this purpose an efficient apparatus for harvesting sunlight. The atomic structure of the apparatus, as it evolved in purple bacteria, has been constructed through a combination of x-ray crystallography, electron microscopy, and modeling. The detailed structure and overall architecture reveals a hierarchical aggregate of pigments that utilizes, as shown through femtosecond spectroscopy and quantum physics, elegant and efficient mechanisms for primary light absorption and transfer of electronic excitation toward the photosynthetic reaction center.

[Gilles de la Tourette's syndrome]. / Gil-de-la-Turetov (Gilles de la Tourette) sindrom.

Gilles de la Tourette's syndrome (GTS) is characterized with motor and vocal tics, initiating before 21 years of age, lasting for over a year and are associated with diverse behavioral disorders. The study analyzes features of 12 our GTS patients with mean age at the onset of the disease of 12.0 years, while the exact diagnosis was established only after 9.5 years (2-33 years). In 11 out of 12 patients the disease started with motor or vocal tics, while in completely developed clinical picture of GTS the permanently present tics were associated with coprolalia (6 patients), echolalia, copropraxia (in 2 patients, respectively), attention deficits (9 patients), obsessive-compulsive disorders (8 patients) etv. The role of neuroleptic therapy was discussed according to our experience and other reported studies. In our study, haloperidol had good therapeutical effect in 64% of the treated patients.