NMR analysis of synthetic human serum albumin alpha-helix 28 identifies structural distortion upon amadori modification

The non-enzymatic reaction between reducing sugars and long-lived proteins in vivo results in the formation of glycation and advanced glycation end products, which alter the properties of proteins including charge, helicity, and their tendency to aggregate. Such protein modifications are linked with various pathologies associated with the general aging process such as Alzheimer disease and the long-term complications of diabetes. Although it has been suggested that glycation and advanced glycation end products altered protein structure and helicity, little structural data and information currently exist on whether or not glycation does indeed influence or change local protein secondary structure. We have addressed this problem using a model helical peptide system containing a di-lysine motif derived from human serum albumin. We have shown that, in the presence of 50 mM glucose and at 37 degrees C, one of the lysine residues in the di-lysine motif within this peptide is preferentially glycated. Using NMR analysis, we have confirmed that the synthetic peptide constituting this helix does indeed form a alpha-helix in solution in the presence of 30% trifluoroethanol. Glycation of the model peptide resulted in the distortion of the alpha-helix, forcing the region of the helix around the site of glycation to adopt a 3(10) helical structure. This is the first reported evidence that glycation can influence or change local protein secondary structure. The implications and biological significance of such structural changes on protein function are discussed

Phonons in potassium doped graphene: the effects of electron-phonon interactions, dimensionality and ad-atom ordering

Graphene phonons are measured as a function of electron doping via the addition of potassium adatoms. In the low doping regime, the in-plane carbon G-peak hardens and narrows with increasing doping, analogous to the trend seen in graphene doped via the field-effect. At high dopings, beyond those accessible by the field-effect, the G-peak strongly softens and broadens. This is interpreted as a dynamic, non-adiabatic renormalization of the phonon self-energy. At dopings between the light and heavily doped regimes, we find a robust inhomogeneous phase where the potassium coverage is segregated into regions of high and low density. The phonon energies, linewidths and tunability are remarkably similar for 1-4 layer graphene, but significantly different to doped bulk graphite.Comment: Accepted in Phys. Rev. B as a Rapid Communication. 5 pages, 3 figures, revised text with additional dat

The Economics of Identity and the Endogeneity of Race

Economic and social theorists have modeled race and ethnicity as a form of personal identity produced in recognition of the costliness of adopting and maintaining a specific identity. These models of racial and ethnic identity recognize that race and ethnicity is potentially endogenous because racial and ethnic identities are fluid. We look at the free African-American population in the mid-nineteenth century to investigate the costs and benefits of adopting alternative racial identities. We model the choice as an extensive-form game, where whites choose to accept or reject a separate mulatto identity and mixed race individuals then choose whether or not to adopt that mulatto identity. Adopting a mulatto identity generates pecuniary gains, but imposes psychic costs. Our empirical results imply that race is contextual and that there was a large pecuniary benefit to adopting a mixed-race identity.

Colorism and African American Wealth: Evidence from the Nineteenth-Century South

Black is not always black. Subtle distinctions in skin tone translate into significant differences in outcomes. Data on more than 15,000 households interviewed during the 1860 federal census exhibit sharp differences in wealth holdings between white, mulatto, and black households in the urban South. We document these differences, investigate the relationships between wealth and the recorded household characteristics, and decompose the wealth gaps into treatment and characteristic effects. In addition to higher wealth holdings of white households as compared to free African-Americans in general, there are distinct differences between both the characteristics of and wealth of free mulatto and black households, whether male- or female-headed. While black-headed households' mean predicted log wealth was only 20% of white-headed households', mulatto-headed households' was nearly 50% that of whites'. The difference between light- and dark-complexion is highly significant in semi-log wealth regressions. In the decomposition of this wealth differential, treatment effects play a large role in explaining the wealth gap between all subpopulation pairs.

The biological effects and properties of K antigens of escherichia coli

Imperial Users onl

Promoting Resiliency: Vicarious Posttraumatic Growth in Trauma Clinicians

Vicarious Posttraumatic Growth (VPG) and Vicarious Traumatization (VT) are two potential outcomes of clinical work with trauma survivors. The aim of this study was to test a predictive model of these constructs, allowing a fuller understanding of preventive strategies clinicians might employ to inoculate themselves against the potential hazards of service provision and provide the highest quality of clinical care. VPG and VT were investigated in 63 self-identified trauma therapists. The results showed that VPG is facilitated by engagement in successful services subsequent to a traumatic event. Self-Care emerged as a poignant buffer against various indices of vicarious traumatization. Other study variables including spiritual beliefs and practices, and years practicing were correlated with vicarious traumatization but failed to reach significance in a majority of regression models due to the small sample size. Directions for future research and practice are discussed

The ammonia, carbon dioxide and water ternary system

Interactions between simple molecules are of fundamental interest across diverse areas of the physical sciences, and the ternary system NH3 +CO2 H2O is no exception. In the outer solar system, interaction of CO2 with aqueous ammonia is likely to occur, synthesising ‘rock-forming’ minerals, with CO2 perhaps playing a role in ammoniawater oceans and cryomagmas inside icy planetary bodies. In the same context, ammonium carbonates may have some astrobiological relevance, since removal of water leads to the formation of urea. On Earth, combination of CO2 with aqueous ammonia has relevance to carbon capture schemes, and there is interest in using such materials for hydrogen storage in fuel cells. Consequently, from earthly matters of climate change to the study of extraterrestrial ices, understanding the structures and properties of ammonium carbonates are important. Despite this, our knowledge of ammonium carbonates is limited, even under ambient conditions of pressure and temperature, and is entirely absent at the higher pressures, severely limiting our ability to model the behaviour of NH3 +CO2 H2O solids and fluids in planetary environments. This work reports the results of several experiments using variable pressure and temperature neutron diffraction work on ammonium bicarbonate [NH4HCO3] and ammonium carbamate [[NH4]+[NH2CO2] – ], with complementary Density Functional Theory (DFT) calculations. The excellent agreement between experiments and DFT calculations obtained so far adds weight to the accuracy of calculated material properties of ammonium carbonate monohydrate [(NH4)2CO2 H2O], ammonium sesquicarbonate monohydrate [(NH4)4(H2(CO3)3) H2O] and several polymorphs of urea [CO(NH2)2] where little empirical data exists. These experimental and computational studies provide the structural and thermoelastic information required for accurate planetary modelling and remote identification of these material on planetary surfaces