The alpha-helix folds more rapidly at the C-terminus than at the N-terminus

The helix-coil dynamics of different sections of an alpha-helical model peptide were observed separately by nanosecond temperature jump experiments with IR detection on a series of isotopically labeled peptides. The results show that the helix-coil dynamics of the alpha-helical C-terminus are faster than those of the N-terminus.     

Cellulose synthesis in maize: isolation and expression analysis of the cellulose synthase (CesA) gene family

Stalk lodging in maize results in significant yield losses. We have determined that cellulose per unit length of the stalk is the primary determinant of internodal strength. An increase in cellulose concentration in the wall might allow simultaneous improvements in stalk strength and harvest index. Cellulose formation in plants can be perturbed by mutations in the genes involved in cellulose synthesis, post-synthetic cellulose alteration or deposition, N-glycosylation, and some other genes with as yet unknown functions. We have isolated 12 members of the cellulose synthase (CesA) gene family from maize. The genes involved in primary wall formation appear to have duplicated relatively independently in dicots and monocots. The deduced amino acid sequences of three of the maize genes, ZmCesA10–12, cluster with the Arabidopsis CesA sequences that have been shown to be involved in secondary wall formation. Based on their expression patterns across multiple tissues, these three genes appear to be coordinately expressed. The remaining genes show overlapping expression to varying degrees with ZmCesA1, 7, and 8 forming one group, ZmCesA3 and 5 a second group, and ZmCesA2 and 6 exhibiting independent expression of any other gene. This suggests that the varying levels of coexpression may just be incidental except in the case of ZmCesA10–12, which may interact with each other to form a functional enzyme complex. Isolation of the expressed CesA genes from maize and their association with primary or secondary wall formation has made it possible to test their respective roles in cellulose synthesis through mutational genetics or transgenic approaches. This information would be useful in improving stalk strength.     

Phase separation in manganites induced by orbital-ordering strains

Doped manganite perovskites AMnO(3) exhibit a rich variety of electronic properties, resulting from the interplay of charge (Mn(3+)/Mn(4+)), spin (Mn magnetic moment) and orbital (Mn(3+) Jahn-Teller distortion) degrees of freedom. Magnetisation measurements and ESR spectra have been used to study a series of eight AMnO(3) perovskites, in which the A cation sites are occupied by a distribution of 70% trivalent lanthanide and 30% divalent Ca, Sr or Ba ions. These all have a mean A cation radius of 1.20 Angstrom but different values of the cation size variance sigma(2). A change from orbital disorder to order (cooperative Jahn-Teller distortions) was previously found in the insulating regime at sigma(2) = approximately 0.005 Angstrom(2). This work has shown that co-existence of the orbitally ordered and disordered phases is found in sigma(2)= 0.0016-0.0040 Angstrom(2) samples, with a difference of 40 K between their Curie temperatures. This is ascribed to competition between orbital ordering and microstructural lattice strains. At larger sigma(2) > 0.005 Angstrom(2), the orbital ordering strains are dominant and only this phase is observed. This intermediate temperature phase segregation is one of many strain-driven separation phenomena in manganites.     

A preliminary observation of additive thermodynamic contribution of pendant arms to the complexation of calixarene derivatives with mercury(II)

An additive thermodynamic contribution of pendant arms to the complexation of calixarene derivatives with mercury(II) in acetonitrile is for the first time demonstrated.