Case Western Reserve University

About: Case Western Reserve University is a education organization based out in Cleveland, Ohio, United States. It is known for research contribution in the topics: Population & Health care. The organization has 54617 authors who have published 106568 publications receiving 5071613 citations. The organization is also known as: Case & Case Western.

The structure of native cellulose

Abstract: Native cellulose has been shown to consist of a crystalline array of parallel chains, based on the X-ray diffraction data for specimens from the sea alga Valonia ventricosa. The unit cell is monoclinic with dimensions a = 16.34 A, b = 15.72 A, c = 10.38 A (fiber axis), and β = 97.0°. The space group is P21 and the cell contains disaccharide segments of eight chains. Models containing chains with the same sense (parallel) or alternating sense (antiparallel) were refined against the intensity data using rigidbody least squares procedures. The results show a preference for a parallel chain structure with specific chain polarity with respect to the c axis. The refinement places the CH2OH side chains approximately 20′ from the so-called tg conformation, with a result that an 02′H…06 intramolecular bond is formed. The structure also contains an 03H…05′ intramolecular bond and an 06H…03 intermolecular bond along the a axis. All these bonds lie in the 020 planes, and the structure is an array of hydrogen-bonded sheets. A major consequence of this work is that regular chain folding can be ruled out and cellulose is seen as extended chain polymer single crystals.

Hydroxyl radical-mediated modification of proteins as probes for structural proteomics.

Abstract: ion of hydrogen from the γ-(C-4) carbon of aliphatic side chains in the presence of oxygen can yield C-2 -C-3 dehydropeptides, via the formation of peroxyl radicals from the γ-carbon-centered radical. 208,210 For example, in the oxidation of the Glu side chain, the γ-carbon peroxyl radical may undergo subsequent reactions leading to the formation of side chain modification products with a mass shift of -30 Da due to decarboxylation; 209,211+14 and+16 Da products; or an unsaturated product, a C-2 -C-3 dehydropeptide (Scheme 4). The dehydropeptide behaves like an oxygenated enol species, which readily undergoes tautomerism to the keto form. This species is easily hydrolyzed to yield two protein fragments: a new amide and a keto acid. 210 Oxidation of aspartic acid seems similar to the case of Glu and may also result in the cleavage of the protein backbone 212 or decarboxylation of a side chain carboxyl group, 211 except at a lower rate than that for Glu. 211 3.2.4. Main Chain Cleavage via Radical Transfer from the â-Carbon at Side Chains Initial hydroxyl radical attack at theâ-carbon (C-3) position can lead to the formation of R-carbon radicals and subsequent main chain rupture. 213,214 In this case, alkoxyl radicals are generated after initial H-abstraction to produce carbon-centered radicals and subsequent reaction with O 2 o give peroxyl radicals (Scheme 5). A number of different pathways may generate alkoxyl radical from different precursors, including termination reactions of the peroxyl species with other radicals and decomposition of the intermediate hydroperoxides. 215,216The alkoxyl radicals can undergoâ-scission at a rate >107 s-1, leading to the loss of a side chain and/or generation of R-carbon radicals and subsequent backbone cleavage. 213,214 The â-scission reaction of alkoxyl radicals appears to be common for aliphatic side chains such as Val, Leu, and Asp,214 resulting in the release of a family of carbonyls including formaldehyde, acetone, isobutyraldehyde, and glyoxylic acids. The rate of suchâ-scission reactions is affected by the nature of the substituents, R and R ′, with the rate of fragmentation increased by the presence of electron releasing alkyl groups and substituents that can stabilize the incipient radical center. The R-carbon radicals generated by the â-scission reaction of alkoxyl radicals are stable due to the delocalization of unpaired electrons onto the neighboring carbonyl and amide functions and relief of steric strain in the alkoxyl radical. 217 Scheme 3. Backbone Cleavage and Side Chain Modification of Pro Hydroxyl Radical-Mediated Modification of Proteins Chemical Reviews, 2007, Vol. 107, No. 8 3527

Commensal Clostridia: leading players in the maintenance of gut homeostasis

Abstract: The gastrointestinal tract is a complex and dynamic network where an intricate and mutualistic symbiosis modulates the relationship between the host and the microbiota in order to establish and ensure gut homeostasis. Commensal Clostridia consist of gram-positive, rod-shaped bacteria in the phylum Firmicutes and make up a substantial part of the total bacteria in the gut microbiota. They start to colonize the intestine of breastfed infants during the first month of life and populate a specific region in the intestinal mucosa in close relationship with intestinal cells. This position allows them to participate as crucial factors in modulating physiologic, metabolic and immune processes in the gut during the entire lifespan, by interacting with the other resident microbe populations, but also by providing specific and essential functions. This review focus on what is currently known regarding the role of commensal Clostridia in the maintenance of overall gut function, as well as touch on their potential contribution in the unfavorable alteration of microbiota composition (dysbiosis) that has been implicated in several gastrointestinal disorders. Commensal Clostridia are strongly involved in the maintenance of overall gut function. This leads to important translational implications in regard to the prevention and treatment of dysbiosis, to drug efficacy and toxicity, and to the development of therapies that may modulate the composition of the microflora, capitalizing on the key role of commensal Clostridia, with the end goal of promoting gut health.

Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 Nanocrystals

Abstract: Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF 4 ) nanocrystals (20-30 nm size) co-doped with the rare earth ions Gd 3+ and Er 3+ /Yb 3+ /Eu 3+ are synthesized and dispersed in water. An efficient up- and downconverted photoluminescence from the rare-earth ions (Er 3+ and Yb 3+ or Eu 3+ ) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two-photon induced process and allowing two-photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two-photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti-claudin-4 and anti-mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd 3+ co-doped within the nanophosphors imparts strong T1 (Spin-lattice relaxation time) and T2 (spin-spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging.