Quantitative analysis using Raman spectrometry.
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Algorithms↗
Biomedical subjects
M J Pelletier
Publications and source records attributed to M J Pelletier.
Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell.
We have demonstrated a sensitivity enhancement factor of 500 in aqueous solutions using a liquid core optical fiber (LCOF) Raman cell made from Teflon-AF. We were able to collect a spectrum of 54 microM lysozyme with a signal-to-noise ratio of 31 in the LCOF Raman cell using 24 mW of laser power and 3 min of integration time. The lysozyme Raman intensity was only 1% of the background Raman intensity from water, but the water-subtracted lysozyme spectrum was still shot-noise-limited and essentially free of nonrandom noise. The lack of nonrandom noise indicates that it should be possible to collect good quality Raman spectra of proteins such as lysozyme at even lower concentrations. The 2.4-microL sample volume of the LCOF Raman cell is an added benefit when limited quantities of sample are available. This volume of a 54 microM lysozyme solution corresponds to only 13 nanomoles or 1.9 microg of lysozyme.
Muramidase↗
Uneven and transient secretin release after a liquid test meal.
In order to test the hypothesis that secretin may be released intermittently after feeding, the plasma secretin concentration was measured at short intervals, and the duodenal pH continuously recorded, after a liquid test meal in 10 human subjects. Secretin was measured with a radioimmunoassay in which the entire molecule is specifically recognized and the immunoreactivities of human secretin and of the porcine peptide used as standard are similar. In the total group, no significant variation of the mean plasma secretin concentration above basal was observed within 45 min after feeding. Analysis of the individual patterns revealed that secretin was released transiently in 5 of the 10 subjects, namely those showing variations of the duodenal pH down to or below 4.0 at some time after the meal. The mean peak delta secretin in these subjects was 7.2 pg ml-1 of plasma. In 7 additional subjects, bolus intravenous injections of 0.005 and 0.01 clinical units kg-1 of porcine secretin resulted in peak delta secretin concentrations of 5.5 and 10.5 pg ml-1, respectively, and were followed by a significant increase of bicarbonate output in the duodenal aspirate. These results indicate that secretin is released unevenly and intermittently in the early period after a liquid meal in man, in amounts that seem sufficient for the initiation of a significant bicarbonate response.
Adult↗
alpha-Fetoprotein screening in patients with idiopathic hemochromatosis and liver cirrhosis.
The serum alpha-fetoprotein level was measured by radioimmunoassay in 200 patients when admitted to hospital, 63 with idiopathic hemochromatosis and 137 with liver cirrhosis. In addition, repeated controls were performed in 19 subjects of each group for a mean period of 11 months (range 3--18 months). Elevated alpha-fetoprotein levels were observed initially or during the study period in 15 patients, a malignant liver tumor being demonstrated in 12 of them. In 4 of these patients, the abnormal alpha-fetoprotein concentration was the clue to the diagnosis of an unsuspected malignant hepatoma, but in none of these cases could the tumor be resected. The present results indicate that screening the serum alpha-fetoprotein level may contribute to the detection of malignant hepatoma in high-risk clinical groups, but the practical interest of such screenings may keep limited until more efficient therapeutic methods are developed.
Adult↗