A further investigation on a MALDI‐based method for evaluation of markers of renal damage

The validity of the urinary protein profile to characterize the pathological states of diabetic, nephropathic and diabetic–nephropathic patients was considered on the basis of previously obtained results by MALDI/MS, showing a different abundance ratio of the collagen α1 and α5 chain precursor fragments at m/z 1219 and 2049 and of the uromodulin precursor fragment at m/z 1912 observed in healthy subjects and patients; a larger number of subjects was examined and the obtained results were statistically evaluated. The p values related to the observed differences indicate that they are statistically significant when comparing all patients versus healthy controls, diabetic with normo or microalbuminuria versus nephropathic with advanced renal disease patients and diabetic with normo or microalbuminuria versus diabetic with advanced nephropathy patients. The scatter plot matrix gives evidence of the strict inverse relationship between the abundances of ions at m/z 1912 and 1219, the correlation coefficient being particularly high (r = 0.921, p < 0.001). The relationship between the true positive rate (sensitivity) and false positive rate (1—specificity) for every possible cutoff value in abundance of the considered ionic species was investigated through the receiver‐operating characteristic (ROC) curve. The obtained data indicate that a good differentiation of nephropathic patients with advanced renal disease and diabetic patients with advanced nephropathy versus healthy subjects can be easily obtained by this approach. Copyright © 2009 John Wiley & Sons, Ltd.     

Isotopic effects due to energy transfer in photechemical reactions

Strong H/D isotopic effects were observed in photochemical decomposition of acetaldehyde and some other organic substances at 77 and 4.2 K. The value of the isotopic effect increased considerably over the temperature range 77 to 4.2 K and remained constant over a wide range of the isotopic molecule ratio as was shown for acetaldehyde. The results obtained were explained in terms of trapping the electron excitation by molecules with lighter isotopes which are known to have, as a rule, lower excitation energy. A theory was developed taking into account the migration of the electron excitation among similar molecules, the energy exchange between two isotopic species, and their photochemical decomposition. The temperature and concentration dependences of the isotopic effects predicted by the theory were in accord with experiment.