Buoyancy of sub-Antarctic notothenioids including the sister lineage of all other notothenioids (Bovichtidae)

The radiation of notothenioid fishes (Perciformes) in Antarctic waters was likely the result of an absence of competition in the isolated Antarctic waters and key traits such as the production of antifreeze glycoprotein and buoyancy modifications. Although notothenioids lack a swim bladder, the buoyancy of Antarctic species, ranging from neutrally buoyant to relatively heavy, corresponds to diverse life styles. The buoyancy of South American notothenioids has not been studied. Static buoyancy was measured in adult notothenioids (n = 263, from six species of the sub-order Notothenioidei, families Bovichtidae, Eleginopidae, Nototheniidae, and Harpagiferidae) from the Beagle Channel. Measurements were expressed as percentage buoyancy (%B). Buoyancy ranged from 3.88 to 6.96% (median, 4.0–6.7%), and therefore, all species could be considered benthic consistent with previous studies that found that neutral buoyancy in notothenioids is rare. Harpagifer bispinis, Patagonotothen cornucola, and Cottoperca gobio were significantly less buoyant than Paranotothenia magellanica. The buoyancy values of most species were concordant with known habitat preferences. These data, especially the data of C. gobio (sister lineage of all other nototehnioids) and E. maclovinus (sister lineage of the Antarctic clade of notothenioids), could be useful for understanding the diversification of this feature during the notothenioid radiation.     

Exocyclic amino groups of flanking guanines govern sequence-dependent adduct conformations and local structural distortions for minor groove-aligned benzo[a]pyrenyl-guanine lesions in a GG mutation hotspot context

The environmental carcinogen benzo[a]pyrene (BP) is metabolized to reactive diol epoxides that bind to cellular DNA by predominantly forming N²-guanine adducts (G*). Mutation hotspots for these adducts are frequently found in 5′-···GG··· dinucleotide sequences, but their origins are poorly understood. Here we used high resolution NMR and molecular dynamics simulations to investigate differences in G* adduct conformations in 5′-···CG*GC··· and 5′-···CGG*C··· sequence contexts in otherwise identical 12-mer duplexes. The BP rings are positioned 5′ along the modified strand in the minor groove in both cases. However, subtle orientational differences cause strong distinctions in structural distortions of the DNA duplexes, because the exocyclic amino groups of flanking guanines on both strands compete for space with the BP rings in the minor groove, acting as guideposts for placement of the BP. In the 5′-···CGG*C··· case, the 5′-flanking G · C base pair is severely untwisted, concomitant with a bend deduced from electrophoretic mobility. In the 5′-···CG*GC··· context, there is no untwisting, but there is significant destabilization of the 5′-flanking Watson–Crick base pair. The minor groove width opens near the lesion in both cases, but more for 5′-···CGG*C···. Differential sequence-dependent removal rates of this lesion result and may contribute to the mutation hotspot phenomenon.     

Purification and analysis of a 5kDa component of enamel matrix derivative

High performance liquid chromatography (HPLC) methods were used to analyse a 5kDa component purified from enamel matrix derivative (EMD), the active ingredient in Emdogain, a commercial product for periodontal tissue regeneration. After initial purification by size-exclusion chromatography (SEC) on a 100 cm x 5 cm column (Bio-Gel P-30 Fine, 280 nm), collected fractions were analysed by size-exclusion HPLC (SE HPLC; TSK-Gel Super SW2000, 220 nm). The fractions containing only the 5kDa component were analysed by reversed-phase high-pressure chromatography (RP HPLC; YMC-Pack ODS-A, 200 nm), revealing four peaks of the 5kDa component. From 1200 mg of EMD (of which 9% is the 5kDa component), approximately 65 mg of lyophilised 5kDa component were obtained, corresponding to a recovery of 60%. The SE HPLC method was mainly suitable for qualitative analysis, whereas the RP HPLC method was appropriate for both qualitative and quantitative analysis.