The S-state dependence of Cl binding to plant Photosystem II

A combined single-turnover flash and ³⁵Cl NMR technique has been used to monitor S-state dependence of Cl⁻ binding to PS-II particles derived from mangrove (Avicennia marina). No detectable high-affinity binding was found to particles in the S₀ and S₁ states, but binding with an affinity comparable to that which activates O₂ evolution was found in the S₂ and S₃ states.     

The neuroscience of grasping

People have always been fascinated by the exquisite precision and flexibility of the human hand. When hand meets object, we confront the overlapping worlds of sensorimotor and cognitive functions. We reach for objects, grasp and lift them, manipulate them and use them to act on other objects. This review examines one of these actions--grasping. Recent research in behavioural neuroscience, neuroimaging and electrophysiology has the potential to reveal where in the brain the process of grasping is organized, but has yet to address several questions about the sensorimotor transformations that relate to the control of the hands.     

pH dependence of the urea and guanidine hydrochloride denaturation of ribonuclease A and ribonuclease T1

To investigate the pH dependence of the conformational stability of ribonucleases A and T1, urea and guanidine hydrochloride denaturation curves have been determined over the pH range 2-10. The maximum conformational stability of both proteins is about 9 kcal/mol and occurs near pH 4.5 for ribonuclease T1 and between pH 7 and 9 for ribonuclease A. The pH dependence suggests that electrostatic interactions among the charged groups make a relatively small contribution to the conformational stability of these proteins. The dependence of delta G on urea concentration increases from about 1200 cal mol-1 M-1 at high pH to about 2400 cal mol-1 M-1 at low pH for ribonuclease A. This suggests that the unfolded conformations of RNase A become more accessible to urea as the net charge on the molecule increases. For RNase T1, the dependence of delta G on urea concentration is minimal near pH 6 and increases at both higher and lower pH. An analysis of information of this type for several proteins in terms of a model developed by Tanford [Tanford, C. (1964) J. Am. Chem. Soc. 86, 2050-2059] suggests that the unfolded states of proteins in urea and GdnHCl solutions may differ significantly in the extent of their interaction with denaturants. Thus, the conformations assumed by unfolded proteins may depend to at least some extent on the amino acid sequence of the protein.     

Distribution of surnames and identities in the Cimbro-Mòcheno communities of Italy

The surnames of populations of the municipalities with Cimbro and Mòcheno origins are compared with each other and with other municipalities of the neighbourhood. This study starts from the supposition that a community of surnames shares a common cultural origin, maintained by reciprocal mobility. The analysis has been carried out by using estimates of the similarities between populations, the topological representations obtained by them and the spatial autocorrelation. On the whole, this research shows no evidence of peculiar distinctions between the populations that share Cimbro and Mòcheno origins compared to the neighbouring ones. Moreover, there is not any evident process of undifferentiated diffusion along all the directions. On the contrary, it is emphasized that belonging to the same geographic region and to the same administrative subdivision mostly influences the similarity between populations. The exception is the Cimbro municipality of Luserna, which presents a peculiar structure of surnames different from other municipalities of the same territory.     

Feminizing chicks: a model for avian sex determination based on titration of Hint enzyme activity and the predicted structure of an Asw-Hint heterodimer

Background  

In birds and some lizards, females are heterogametic with a ZW karyotype, while males are ZZ homogametes. The molecular basis for sexual differentiation in birds is unknown: arguments exist for doses of Z masculinizing chicks and for W information feminizing. ASW was identified as a tandemly repeated gene conserved on avian W chromosomes that is expressed in early female development and appears to be an inactive form of avian Z-encoded HINT. Hint is a dimeric enzyme that hydrolyzes AMP linked to lysine, whose enzyme activity is required for regulation of the Cdk7 homologous Kin28 kinase in yeast. Of 16 residues most conserved across all life forms for AMP interactions, 15 are sexually dimorphic in birds, that is, altered in the female-specific Asw protein. Genomic and expression data suggest that Asw may feminize chicks, dominantly interfering with Hint function by heterodimerization.     

Somatic embryogenesis from three commercially important inbreds of Zea mays

Zea mays (maize) genotypes B73, Mo17 and LH38 were evaluated for their capacity to undergo somatic embryogenesis. Over 1500 immature embryos (ie's) of B73, 2900 ie's of LH38 and 400 ie's of Mo17 were excised 10–17 days after pollination and plated on six different media. Overall response, reported as a percentage of the ie's plated that developed embryogenic callus, was 2.1%, 1.6% and 26% for LH38, B73 and Mo17, respectively. Best response on a given medium for each of these genotypes was 9.2% (LH38), 4.4% (B73) and 100% (Mo17). Other parameters examined for their effects on production of embryogenic callus included self vs. sib pollination, ear ranking (1st, 2nd or 3rd ear), and temperature shock, all of which had no significant effect. Plantlets regenerated from selected treatments of B73 have been grown to maturity, selfed or sibbed and seed collected for field evaluation.Abbreviations i.e. immature embryo - 2,4-D 2,4-di-chlorophenoxyacetic acid     

DNA strand breaks in ejaculated human spermatozoa: comparison of susceptibility to the nick translation and terminal transferase assays

The nick translation and terminal transferase assays have been compared to test their relative efficiency in detecting DNA breakage in ejaculated human spermatozoa. The results have been correlated with the percentage of chromomycin A3 positive sperm, a fluorochrome that is indicative of the protamination state of sperm. Examination of the ejaculated sperm of 30 subjects revealed that the percentage of positivity to the nick translation and terminal transferase assays did not differ, even when using different fixatives. It is concluded that the inability of the two assays to distinguish the type of DNA damage, as is possible in somatic nuclei, is most probably linked to the unique nature of sperm chromatin. It is proposed that the presence of the damaged DNA may be the remnants of an imperfect spermiogenesis, probably related to an inadequate protamine deposition. This is supported by the strong correlation between the presence of DNA damage and underprotamination as evidenced by chromomycin A3. © Chapman & Hall     

Wired to be social: the ontogeny of human interaction

Background

Newborns come into the world wired to socially interact. Is a propensity to socially oriented action already present before birth? Twin pregnancies provide a unique opportunity to investigate the social pre-wiring hypothesis. Although various types of inter-twins contact have been demonstrated starting from the 11^th week of gestation, no study has so far investigated the critical question whether intra-pair contact is the result of motor planning rather then the accidental outcome of spatial proximity.

Methodology/Principal Findings

Kinematic profiles of movements in five pairs of twin foetuses were studied by using four-dimensional ultrasonography during two separate recording sessions carried out at the 14^th and 18^th week of gestation. We demonstrate that by the 14th week of gestation twin foetuses do not only display movements directed towards the uterine wall and self-directed movements, but also movements specifically aimed at the co-twin, the proportion of which increases between the 14^th and 18^th gestational week. Kinematic analysis revealed that movement duration was longer and deceleration time was prolonged for other-directed movements compared to movements directed towards the uterine wall. Similar kinematic profiles were observed for movements directed towards the co-twin and self-directed movements aimed at the eye-region, i.e. the most delicate region of the body.

Conclusions/Significance

We conclude that performance of movements towards the co-twin is not accidental: already starting from the 14th week of gestation twin foetuses execute movements specifically aimed at the co-twin.