Microwave - Assisted Derivatization of Glucose and

Federal Ministry of Education and Research (BMBF): Kompetenznetz Demenzen (01 GI 0420) and HBPP-NGFN2 (01 GR 0447). We gratefully appreciate the technical help of Christine Schö del. protein phosphorylated at threonine 181 in CSF as a neurochemical bi-omarker in Alzheimer's disease: original data and review of the literature. Highly conserved and disease-specific patterns of carboxyterminally truncated A␤ peptides 1–37/38/39 in addition to 1– 40/42 in Alzheimer's disease and in patients with chronic neuroinflammation.tion of ␤-amyloid peptide 2– 42 in sporadic and familial Alzheimer's disease and its generation in PS1 knockout cells. Evaluation of CSF-tau and CSF-A␤42 as diagnostic markers for Alzheimer disease in clinical practice. High cerebrospinal fluid tau and low amyloid ␤42 levels in the clinical diagnosis of Alzheimer disease and relation to apolipoprotein E genotype.spinal fluid markers for prediction of Alzhei-mer's disease. amyloid ␤ peptide patterns in Alzheimer's disease patients and nondemented controls depend on sample pretreatment: Indication of carrier-mediated epitope masking of amyloid ␤ Effects of processing and storage conditions on amyloid ␤ (1– 42) and tau concentrations in cerebrospinal fluid: implications for use in clinical practice. Standardization of measurement of ␤-amy-loid(1– 42) in cerebrospinal fluid and plasma. To the Editor: Monosaccharides are usually analyzed by use of automatic monitors or enzymatic immunoassays. However , gas chromatography (GC) is an accurate and precise technique for galactose quantification (1), and it is regarded as a reference method for glucose (2). GC procedures require a long derivatization time in 2 consecutive reactions of 60 –90 min to generate the aldonitrile pentaacetate derivative. Fast derivatization techniques are often requested today because the bottleneck for sample throughput has moved from analysis to sample preparation. Recently, we dramatically decreased the derivati-zation time for sugars (mono-and disaccharides) in GC analysis (3) by using trimethylsilyl-oxime derivatives. This derivative, however, gives 2 peaks in the chromatogram, which is acceptable for the glucose–fructose pair but not for the glucose– galac-tose pair. In this study, we optimized the aldonitrile pentaacetate deriva-tivization step, using microwave-assisted conditions to obtain single-peak derivatives for each sugar. Plasma from healthy adults was used as a model matrix for the recovery experiments. Glucose and galactose were from Sigma. Plasma samples were prepared as follows: we deproteinized 200 ␮L of plasma with 500 ␮L of methanol. After centrifugation at 5000g, the supernatant was withdrawn and evaporated to dryness under a stream of nitrogen. We added 100 ␮L of hydroxylamine hy-drochloride (20 g/L in pyridine) …