A method was developed to distinguish both the linkage position and the anomericity of all reducing and two nonreducing glucopyransosyl-glucose disaccharides using only electrospray ionization-mass spectrometry/mass spectrometry (ESI-MS/MS). Carbohydrates are well-known to form complexes with metal cations during electrospray ionization. Addition of a lithium salt to a solution containing a disaccharide, M, results in [M + Li] after ESI. Collision-induced dissociation of these ions creates product ions at m/z 187 and m/z 169 from cleavage of the glycosidic bond and are present for all disaccharides studied. Both of these product ions were found to adduct water after their formation in a quadrupole ion trap. The kinetics of this water adduction can be measured by isolating either of the product ions and waiting a short time (<1 s) before mass analysis. Additionally, for both product ions, only a fraction of the ions were able to adduct water. This unreactive fraction was measured along with the reaction rate, and the combination of these two values was found to be unique for each disaccharide. Additionally, after CID, a 1000 ms delay can be added, and the ratios of the resulting products ions of m/z 169, 187, and 205 can be used to distinguish linkage position and anomericity with a single tandem mass spectrometry experiment.
A method to distinguish the four most common biologically relevant underivatized hexoses, d-glucose, d-galactose, d-mannose, and d-fructose, using only mass spectrometry with no prior separation/derivatization step has been developed. Electrospray of a solution containing hexose and a lithium salt generates [Hexose+Li]. The lithium-cationized hexoses adduct water in a quadrupole ion trap. The rate of this water adduction reaction can be used to distinguish the four hexoses. Additionally, for each hexose, multiple lithiation sites are possible, allowing for multiple structures of [Hexose+Li]. Electrospray produces at least one structure that reacts with water and at least one that does not. The ratio of unreactive lithium-cationized hexose to total lithium-cationized hexose is unique for the four hexoses studied, providing a second method for distinguishing the isomers. Use of the water adduction reaction rate or the unreactive ratio provides two separate methods for confidently (p ≤ 0.02) distinguishing the most common biologically relevant hexoses using only femtomoles of hexose. Additionally, binary mixtures of glucose and fructose were studied. A calibration curve was created by measuring the reaction rate of various samples with different ratios of fructose and glucose. The calibration curve was used to accurately measure the percentage of fructose in three samples of high fructose corn syrup (<4% error).
A method has been developed that is capable of distinguishing an exhaustive list of underivatized D-pentoses with only a mass spectrometer. Electrospray ionization (ESI) of a solution containing a pentose and a lithium salt yields [Pentose + Li]. These lithiated pentoses adduct water in a quadrupole ion trap. The reaction rate of water adduction is unique for several of the pentose isomers. Additionally, there are multiple potential gas-phase lithiation sites to form [Pentose + Li]. A mixture of ions with at least one reactive (water adducting) and at least one unreactive (non-adducting) lithiation site is formed for each pentose. The water adduction reaction rate along with the unreactive fraction of lithiated pentose can be used to completely discriminate all D-pentoses. Graphical Abstract ᅟ.
Specific organochlorines (OCs) have been associated with non‐Hodgkin lymphoma (NHL) with varying degrees of evidence. These associations have not been evaluated in Asia, where the high exposure and historical environmental contamination of certain OC pesticides (e.g., dichlorodiphenyltrichloroethane [DDT], hexachlorocyclohexane [HCH]) are different from Western populations. We evaluated NHL risk and prediagnostic blood levels of OC pesticides/metabolites and polychlorinated biphenyl congeners in a case–control study of 167 NHL cases and 167 controls nested within three prospective cohorts in Shanghai and Singapore. Conditional logistic regression was used to analyze lipid‐adjusted OC levels and NHL risk. Median levels of p,p′‐dichlorodiphenyldichloroethylene (p,p′‐DDE), the primary DDT metabolite, and β‐HCH were up to 12 and 65 times higher, respectively, in samples from the Asian cohorts compared to several cohorts in the United States and Norway. An increased risk of NHL was observed among those with higher β‐HCH levels both overall (3rd vs. 1st tertile OR = 1.8, 95%CI = 1.0–3.2; ptrend = 0.049) and after excluding cases diagnosed within 2 years of blood collection (3rd vs. 1st tertile OR = 2.0, 95%CI = 1.1–3.9; ptrend = 0.03), and the association was highly consistent across the three cohorts. No significant associations were observed for other OCs, including p,p′‐DDE. Our findings provide support for an association between β‐HCH blood levels and NHL risk. This is a concern because substantial quantities of persistent, toxic residues of HCH are present in the environment worldwide. Although there is some evidence that DDT is associated with NHL, our findings for p,p′‐DDE do not support an association.
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