A cluster of cooperating tumor-suppressor gene candidates in chromosomal deletions

The large chromosomal deletions frequently observed in cancer genomes are often thought to arise as a "two-hit" mechanismin the process of tumor-suppressor gene (TSG) inactivation. Using a murine model system of hepatocellular carcinoma (HCC) and in vivo RNAi, we test an alternative hypothesis, that such deletions can arise from selective pressure to attenuate the activity of multiple genes. By targeting the mouse orthologs of genes frequently deleted on human 8p22 and adjacent regions, which are lost in approximately half of several other major epithelial cancers, we provide evidence suggesting that multiple genes on chromosome 8p can cooperatively inhibit tumorigenesis in mice, and that their cosuppression can synergistically promote tumor growth. In addition, in human HCC patients, the combined down-regulation of functionally validated 8p TSGs is associated with poor survival, in contrast to the down-regulation of any individual gene. Our data imply that large cancer-associated deletions can produce phenotypes distinct from those arising through loss of a single TSG, and as such should be considered and studied as distinct mutational events

Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids

The origin of microstrain broadening in X-ray diffraction patterns of nanocrystalline metals is investigated by comparing data obtained from Virtual diffractograms and from direct analysis of computer-generated samples. A new method is introduced that allows the local deformation gradient to be calculated for each lattice site in the microstructure from atomic coordinates obtained by molecular dynamics simulations. Our results reveal that microstrain broadening in undeformed samples cannot be attributed to lattice dislocations or strain fields near grain boundaries. The broadening arises, instead. from long-range correlated displacement fields that extend throughout the grains. The microstrain therefore provides a quantitative measure for distortions far from grain boundaries. This suggests that diffraction-based strategies for inferring the dislocation density in ultrafine-grained metals do not necessarily apply to nanocrystalline materials. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Needle-free vaccination: formulation and dermal delivery of diphtheria toxin CRM197 mutant

The unsafe use of needles propagates cross infections with bloodborne pathogens and reduces the positive impact of vaccinations on global health. While a plethora of needle-free injection devices exist, the reformulation of protein-based vaccines is largely empirical and costly, which presents a barrier to their widespread clinical application. This thesis contributes to the identification of approaches that facilitate rapid vaccine reformulation and enhance the immunogenicity of needle-free dry-powder vaccines with the help of novel antigen delivery platforms. We hypothesised that the thermodynamic stabilisation of diphtheria toxin mutant 197 (CRM197), a glycoconjugate vaccine carrier protein, may enhance its structural preservation during spray-freeze-drying (SFD), and that its formulation in either soluble, surface-adsorbed, or nanoparticle form impacts the elicited immune response. Differential scanning fluorimetry was used to study the effect of excipients on the thermal stability of CRM197. Dry-powder formulation of CRM197 used i) encapsulation into a thermodynamically stabilising excipient matrix by SFD, ii) surface-immobilisation via physisorption onto a novel potassium-doped hydroxyapatite (kHA) carrier microparticle formed by molten salt synthesis, and iii) chemical conjugation and surface presentation on amphiphilic block copolymer nanoparticles that were incorporated into SFD-powders (SFD-NP). The structural integrity of CRM197 was assessed by size separation in addition to various spectral and thermal analysis methods. The immunogenicity of dry-powder CRM197 formulations was subsequently tested in vivo. The results suggest that the thermodynamic stability of CRM197 in solution does not ensure its structural stability during SFD. While needle-free dermal vaccination with kHA-adsorbed CRM197 induced comparable antibody titres to conventional IM injection of alum-adjuvanted CRM197, needle-free SFD and SFD-NP powders were less immunogenic. The highest mean IgG titre and most balanced Th1/Th2 response was achieved with nanoparticle-conjugated CRM197 by IM, which outperformed the current clinical standard. Therefore, future vaccine design should combine thermodynamic and kinetic stability screening, and place special emphasis on the delivery and structural presentation of the antigen to the immune system.This thesis is not currently available in ORA

Line stress of step edges at crystal surfaces

Step edges at crystal surfaces interact elastically with the underlying bulk solid. The resulting attraction or repulsion between neighboring steps is well described by an established dipole model. Here, we focus on the average stress which a step edge generates in the bulk. This quantity represents an excess of surface stress due to the presence of the step. Within the standard dipole description of the stress field of steps, that excess is zero. Yet, atomistic simulation testifies to a significant variation in the apparent surface stress of vicinal surfaces with the number density of steps. We show how a line stress can be defined as an excess in surface stress per line length. The definition is analogous to that of line tension as an excess of surface tension. Even though the step edge may be viewed as a one-dimensional object, we show that the line stress cannot be represented by a vector along the line; it is also not adequately represented by dipole forces. The line stresses give rise to cusps, typically upward, in polar plots of the principal values of the surface stress tensor in the surface orientation domain. We present a continuum model that links the directionality and magnitude of the line stress to the surface stress at the inclined step face. (C) 2011 Elsevier B.V. All rights reserved

Ab initio study of surface stresses of charged Au films

It has been observed in experiments that charging of nanometer-sized porous material can lead to expansion or contraction of this material. This effect can be explained by a change in surface stress as a function of surface electron charge density. Here, we employ ab initio density functional calculations using a mixed-basis pseudopotential approach to study the change in surface stresses, f, as a function of surface charge density, q for Au thin films with (111) and (100) surfaces. The derivative of the surface stress with respect to the charge, f/q, at equilibrium is related to and can be evaluated from /e of an uncharged slab, where is the chemical potential of the electrons in the slab and e the tangential strain. The responses of the (111) and (100) surfaces to charging are evaluated in this way as -1.86 V and -0.90 V, respectively. The calculated values compare well to experimental observations (-0.9 V)