Partial trisomy 20p resulting from a recombination of a familial pericentric inversion

Summary Recombination of an inherited pericentric inversion of chromosome 20 has given rise to a child with partial trisomy 20p. To our knowledge no previous familial inversions of this chromosome have been described in the literature.     

Solid-state 15N NMR of oriented lipid bilayer bound gramicidin A'

Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28 degrees C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +/- 3 degrees. Uniformly 15N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing 15N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution 15N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. These bond orientations are only partially consistent with the extant structural models of gramicidin.     

Effect of iodide on estrogen-induced uterine peroxidase

Iodide administered in the drinking water for 5–7 days increased the activity of estradiol-induced uterine peroxidase in the immature rat. This effect was specific for iodide and could not be mimicked by chloride, bromide, thiocyanate, perchlorate or iodate. Sodium iodide also increased peroxidase activity in the parotid gland but had no effect on glucose-6-phosphate dehydrogenase in the uterus, thyroid or parotid even though estradiol produced a 2-fold increase in the activity of this enzyme in the uterus. ¹²⁵I was taken up more readily by the uterus than by muscle but this process was not influenced by prior treatment of the animals with estrogen. The in vitro effect of sulfhydryl reagents on uterine peroxidase was also investigated and proposals made for possible mechanisms of action of iodide on this enzyme in the intact animal.     

Role of methyl groups in dynamics and evolution of biomolecules

Recent studies have discovered strong differences between the dynamics of nucleic acids (RNA and DNA) and proteins, especially at low hydration and low temperatures. This difference is caused primarily by dynamics of methyl groups that are abundant in proteins, but are absent or very rare in RNA and DNA. In this paper, we present a hypothesis regarding the role of methyl groups as intrinsic plasticizers in proteins and their evolutionary selection to facilitate protein dynamics and activity. We demonstrate the profound effect methyl groups have on protein dynamics relative to nucleic acid dynamics, and note the apparent correlation of methyl group content in protein classes and their need for molecular flexibility. Moreover, we note the fastest methyl groups of some enzymes appear around dynamical centers such as hinges or active sites. Methyl groups are also of tremendous importance from a hydrophobicity/folding/entropy perspective. These significant roles, however, complement our hypothesis rather than preclude the recognition of methyl groups in the dynamics and evolution of biomolecules.     

Molecular evidence for the polyphyly of Olearia (Astereae: Asteraceae)

 Analyses of ITS sequences for 49 species of Olearia, including representatives from all currently recognised intergeneric sections, and 43 species from 23 other genera of Astereae, rooted on eight sequences from Anthemideae, provide no support for the monophyly of this large and morphologically diverse Australasian genus. Eighteen separate lineages of Olearia are recognised, including seven robust groups. Three of these groups and another eight species are placed within a primary clade incorporating representatives of Achnophora, Aster, Brachyscome, Calotis, Camptacra, Erigeron, Felicia, Grangea, Kippistia, Lagenifera, Minuria, Oritrophium, Peripleura, Podocoma, Remya, Solidago, Tetramolopium and Vittadinia. The remaining four groups and three individual species lie within a sister clade that also includes Celmisia, Chiliotrichum, Damnamenia, Pleurophyllum and Pachystegia. Relationships within each primary clade are poorly resolved. There is some congruence between this molecular estimate of the phylogeny and the distribution of types of abaxial leaf-hair, which is the basis of the present sectional classification of Olearia, but all states appear to have arisen more than once within the tribe. It is concluded that those species placed within the second primary clade should be removed from the genus, but the extent to which species placed within the first primary clade constitute a monophyletic group can only be resolved with further sequence data. Received November 12, 2001; accepted April 29, 2002 Published online: November 22, 2002 Addresses of authors: Edward W. Cross, Centre for Plant Biodiversity Research, CSIRO, GPO Box 1600, Canberra, ACT 2601, Australia (E-mail: ed.cross@csiro.au); Christopher J . Quinn, Royal Botanic Gardens, Mrs Macquaries Rd., Sydney, NSW 2000, Australia; Steven J. Wagstaff, Landcare Research, PO Box 69, Lincoln 8152, New Zealand.     

Structural and functional variability among DQ β alleles of DR2 subtypes

Homozygous lymphoblastoid cell lines representing various Dw subtypes of DR2 were examined for polymorphism at the DQ locus by molecular and cellular techniques. The subtypes studied included Dw2, Dw12, and a group heterogenous by cellular typing that we shall refer to as non-Dw2/non-Dw12. Restriction fragment length polymorphism analysis of cell lines representing these subtypes revealed DQ -specific patterns consistent with cellular typing. Two-dimensional gel electrophoresis of DQ molecules from representative cell lines revealed a structural polymorphism of DQ among the three subtypes. The DQ chain migrated to a position that was unique to each subtype and was consistent among various representative cell lines of each subtype. Nucleotide sequence analysis of cDNA clones of DQ from Dw2, Dw12, and non-Dw2/non-Dw12 lines confirmed that the variability resided at the genetic level. Variability was found in the form of numerous scattered nucleotide substitutions throughout the first domain of these alleles. The DQ gene of the non-Dw2/non-Dw12 cell line AZH was further found to be almost identical with the DQ gene of a DR1 line (Bell et al. 1985b), implicating a common evolutionary origin of these alleles. The only difference between these two sequences was due to an apparent gene conversion event at amino acid 57. T-cell cloning experiments resulted in the derivation of Epstein-Barr virus-specific, DQw1-restricted clones that proliferated against only those cell lines that exhibited the DQ gene common to AZH and the DR1 cell line. Thus, the polymorphism among DQ alleles within DR2 results in subtype-specific restriction.