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Ammonium-based alkali-catalyzed [beta]-elimination under nonreducing conditions was investigated in detail for the stability of the released mucin-type O-glycan chains with [beta]1,3-1inked cores. In contrast to the previously studied [beta]1,4-linkage of the N-glycan-type, which was shown to be stable under the ammonium-based alkaline conditions, the [beta]l,3-linkaga is labile toward alkaline treatment and considerable peeling was observed with both model heptasaccharides and standard glycoproteins. The former include eight reducing glucoheptasaccharides with different and commonly occurring linkages ([alpha]l,2-, [beta]1,2-, [alpha]l,3-,[beta]1,3-, [alpha]l,4-, [beta]1,4-, [alpha]1,6-, and [beta]l,6-linkages), and the latter include mucin-type bovine submaxillary mucin and bovine fetuin, which contains both O-and N-glycans. The results indicated that complete prevention of peeling under nonreducing alkali-catalyzed hydrolysis conditions remains difficult. The yields of released O-and N-glycans were also assessed by use of the two glycoproteins as models. Compared with conventional procedures, Carlson degradation for O-glyean release and PNGase F digestion for N-glycan release, the nonreducing ammonium-based alkaline hydrolysis gave lower yields. Great care has to be taken when employing such nonreducing alkaline conditions in glycomic analysis and in obtaining glycoprotein glycans for functional studies. 10.1021/ac102300r

The Asian interior has the largest mid-latitude arid zone in the Northern Hemisphere, and so has become increasingly attractive for studying the initiation and the past extent of aridification in this zone. Given the enormousness of the Asian interior, it remains unclear how old and extensive the eolian deposits might have been, and what wind regimes have been responsible for the formation of the mid-latitude arid zone. Here we report new eolian records of widespread Tertiary eolian deposits in a region far from the Chinese Loess Plateau, the giant Junggar inland basin of northwestern China. Our results demonstrate that the earliest eolian deposition initiated ca. 24 Ma. We interpret that the Tertiary eolian dust in the Junggar Basin was transported by westerly winds, possibly from areas in Kazakhstan; the dust differs from the airborne dust transported by winter monsoon winds from the deserts of Mongolia and northern China that accumulated on the Loess Plateau. These results further reveal that the climate pattern, similar to that of the present, has prevailed at least since the latest Oligocene in Central Asia. doi: 10.1130/G30776.1

The Tianshan Range is one of the longest and highest mountain belts in Central Asia, stretching east-west for ~2500 km. Uplift of this late Paleozoic orogenic belt resulted from intracontinentai deformation caused by the collision of the Indian and Eurasian plates during the Cenozoic era. To constrain the timing of Cenozoic tectonic deformation of the Tianshan Range, we analyzed the magnetostratigraphy of 3780-m-thick Neogene deposits from the Kuqa foreland basin of southern Tianshan. The geometry measurements and magnetic fabric data show that syntectonic growth strata began to accumulate at ~6.5 Ma ago, indicating that crustal shortening initiated in the latest Miocene. The increase in sedimentation rate and an abrupt change of the magnetic fabric parameters also occurred at 6.5 Ma, accompanied by onset of syntectonic growth strata. The latest Miocene crustal shortening is a significant tectonic event in the foreland basin of the southern Tianshan Range in response to the India-Eurasia collision. doi: 10.1130/G30278A.1

The glycosaminoglycan (GAG) family of biomacromolecules is composed acidic and linear chains of repeating disaccharide units. Quantitative disaccharide composition analysis is essential for the study and characterization of GAGs. Heparan sulfate and heparin consist of multiple disaccharide units and can be well-separated by ion-pairing reversed-phase microflow high-performance liquid chromatography (IPRP-Mf-HPLC). Each disaccharide can be detected and its mass confirmed by electrospray ionization mass spectrometry (ESI-MS). Isotopically enriched disaccharides were prepared chemoenzymatically from a uniformly [sup.13]C,[sup.15]N-labeled N-acetylheparosan (-GlcA(I[right arrow]4)GlcNAc-) obtained from the fermentation of E. coli K5. These isotopically enriched disaccharides have identical HPLC retention times and mass spectra as their unlabeled counterparts and were used in liquid chromatography--mass spectrometry (LC--MS) as internal standards. The ratio of intensifies between each pair of enriched and nonenriched disaccharides showed a linear relationship as a function of concentration. With the use of these calibration curves, the amount of each disaccharide ([greater than or equal to] 2 ng/ disaccharide) could be quantified in four heparan sulfate samples analyzed by this method.

The Taklimakan Desert is the world's second-largest shifting sand desert, located in the rain shadow of the Tibetan Plateau. The initiation of desert formation in the Asian interior is one of the most prominent climate changes in the Northern Hemisphere during the Cenozoic Era. Dating the earliest formation of this desert is important for understanding the climatic effects of the uplifted Tibetan Plateau. Here we report 1071-m-thick Neogene deposits with intercalated eolian dune sands from the only outcrop in the central Taklimakan Desert. Based on paleomagnetic measurements, biostratigraphic age control, and previous electron spin resonance dating results, the oldest in situ eolian dune sands were confirmed to be ca. 7 Ma, much older than the previous reported wind-blown siltstone from the southern edge of the Taklimakan Desert. This new result indicates that desert conditions initiated ca. 7 Ma in the center of the Tarim Basin. We attribute this event to the late Cenozoic climatic deterioration and/or to the rain-shadow effect caused by late Miocene uplift of the northern Tibetan margin.