Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs.

The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

Genetic analysis of 56 polymorphisms in 17 genes involved in methionine metabolism in patients with abdominal aortic aneurysm.

BACKGROUND: Previous studies suggested an association between abdominal aortic aneurysm (AAA) and hyperhomocysteinaemia, a complex trait determined by genetic and environmental factors. Our hypothesis was that polymorphisms in genes directly or indirectly involved in methionine metabolism may contribute to AAA susceptibility. METHOD: We studied 56 polymorphisms in MTHFR, MTR, MTRR, CBS, MTHFD1, SLC19A1, NNMT, TCN2, AHCY, BHMT, BHMT2, FOLH1, TYMS, ENOSF1, SHMT1, PON1, PON2 genes according to their demonstrated/putative function, localisation in promoter or regulatory and coding regions and/or heterozygosity values >0.300. Polymorphisms were evaluated by using a primer extension based microarray technology in 423 AAA patients and 423 matched controls. RESULTS: All polymorphisms resulted in Hardy-Weinberg equilibrium in patients and controls. At the multiple logistic regression analysis adjusted for traditional cardiovascular risk factors (sex, age, hypertension, smoking habit, dyslipidaemia, diabetes) and chronic obstructive pulmonary disease (COPD), rs8003379 MTHFD1 (odds ratio (OR) 0.41, 95% confidence interval (CI) 0.26 to 0.65) and rs326118 MTRR (OR 0.47, 95% CI 0.29 to 0.77) polymorphisms resulted in independent susceptibility factor for AAA. CONCLUSIONS: After haplotype reconstruction, logistic regression analyses adjusted for traditional risk factors and COPD showed a significant association among AAA and AHCY, FOLH1, MTHFD1, MTR, NNMT, PON1 and TYMS haplotypes. Our findings offer new insights into the pathogenesis of AAA.

[Anatomo-pathologic findings in 2 cases of Burkitt's lymphoma of the jaw]. / Rilievi anatomo-patologici su due casi di linfoma di Burkitt a sede mascellare.

The various types of Burkitt's lymphomas are classified with a review of their main clinical and histological features and particular reference to the Middle Eastern form.