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首页> 外文期刊>Marine Chemistry >Molecular level characterization of methyl sugars in marine high molecular weight dissolved organic matter
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Molecular level characterization of methyl sugars in marine high molecular weight dissolved organic matter

机译：海洋高分子量溶解有机物中甲基糖的分子水平表征

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Dissolved organic matter (DOM) is the largest active organic carbon reservoir in the ocean (662 GT C), a major fraction (>95%) of which remains chemically uncharacterized. The concentration and isolation of DOM from seawater by ultrafiltration facilitates its chemical characterization by spectroscopic techniques. Using ultrafiltration, silver cation preparative chromatography and gas chromatography coupled with mass spectrometry (GC-MS), we identified 50 novel sugar compounds after hydrolysis of the high molecular weight dissolved organic matter fraction (HMWD0M; the fraction of DOM isolated after ultrafiltration). Sugars were identified by comparison of their mass spectra with those of chemically synthetized standards and with spectra previously described in the literature. Our results showed that mono- and di-methylated hexoses; mono- and di-methylated pentoses; mono- and di-methylated 6-deoxysugars, as well as heptoses, methylated heptoses, 3,6-dideoxysugars and 1,6 anhydrosugars (levoglucosan, mannosan, and galactosan) are components of HMWD0M, which may explain the low apparent yields of sugars recovered by molecular level (HPLC) analyses of HMWD0M after hydrolysis. From three depths spanning the surface (15 m) to bathypelagic (1800 m) ocean in the North Pacific near Hawaii our results showed that mono- and di-methylated hexoses were most abundant in the surface sample (64% of the total identified methylated sugar compounds), while at 1800 m monomethylated 6-deoxysugars were the dominant sugars (42% of the total identified methylated sugar compounds). The high diversity of mono- and di-methylated hexoses in the surface sample most likely suggests an algal and/or bacterial source, while the high abundance of methylated 6-deoxy hexoses in the deep sample points toward an important bacterial contribution because the latter sugars are mostly found in bacterial lipopolysaccharides as well as highly degraded organic material.
机译：溶解有机物（DOM）是海洋中最大的活性有机碳储集层（662 GT C），其中大部分（> 95％）仍未化学表征。通过超滤从海水中浓缩和分离DOM有助于通过光谱技术对其化学特征进行表征。使用超滤，银阳离子制备色谱和气相色谱结合质谱（GC-MS），我们在水解高分子量溶解有机物组分（HMWD0M；超滤后分离出的DOM组分）后，鉴定了50种新型糖化合物。通过将糖的质谱图与化学合成标准品的质谱图以及先前文献中描述的质谱图进行比较，可以鉴定出糖。我们的结果表明，单和二甲基化的己糖；单和二甲基化戊糖;一甲基和二甲基化的6-脱氧糖以及庚糖，甲基化的七糖，3,6-二脱氧糖和1,6脱水糖（左旋葡聚糖，甘露聚糖和半乳糖聚糖）是HMWD0M的成分，这可能解释了糖的低表观产量水解后通过HMWD0M的分子水平（HPLC）分析回收。从横跨夏威夷附近北太平洋海表层（15 m）到深海（1800 m）的三个深度，我们的结果表明，单甲基化和二甲基化的己糖在表面样本中含量最高（占已鉴定的甲基化糖总量的64％）化合物，而在1800 m处，单甲基化的6-脱氧糖是主要的糖类（占总甲基化糖类化合物的42％）。表面样品中单甲基化和二甲基化己糖的高度多样性很可能暗示了藻类和/或细菌的来源，而深层样品中甲基化的6-脱氧己糖的高丰度则表明细菌的重要贡献，因为后者的糖分细菌脂多糖和高度降解的有机物质中最常见。

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