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Naturally occurring and chemically engineered modifications are among the most powerful strategies explored for fine-tuning the conformational characteristics and intrinsic stability of nucleic acids topologies. Modifications at the 2′-position of the ribose or 2′-deoxyribose moieties differentiate nucleic acid structures and have a significant impact on their electronic properties and base-pairing interactions. 2′-O-Methylation, a common post-transcriptional modification of tRNA, is directly involved in modulating specific anticodon–codon base-pairing interactions. 2′-Fluorinated and arabino nucleosides possess novel and beneficial medicinal properties and find use as therapeutics for treating viral diseases and cancer. However, the potential to deploy 2′-modified cytidine chemistries for tuning i-motif stability is largely unknown. To address this knowledge gap, the effects of 2′-modifications including O-methylation, fluorination, and stereochemical inversion on the base-pairing interactions of protonated cytidine nucleoside analogue base pairs, the core stabilizing interactions of i-motif structures, are examined using complementary threshold collision-induced dissociation techniques and computational methods. The 2′-modified cytidine nucleoside analogues investigated here include 2′-O-methylcytidine, 2′-fluoro-2′-deoxycytidine, arabinofuranosylcytosine, 2′-fluoro-arabinofuranosylcytosine, and 2′,2′-difluoro-2′-deoxycytidine. All five 2′-modifications examined here are found to enhance the base-pairing interactions relative to the canonical DNA and RNA cytidine nucleosides with the greatest enhancements arising from 2′-O-methylation and 2′,2′-difluorination, suggesting that these modifications should well be tolerated in the narrow grooves of i-motif conformations. [ABSTRACT FROM AUTHOR]

Jonathan J Streit,1 Yousef Shishani,1 Mark Rodgers,2 Reuben Gobezie1 1The Cleveland Shoulder Institute, 2Department of Pathology, University Hospitals of Cleveland, Cleveland, OH, USA Background: Bicipital tendinitis is a common cause of anterior shoulder pain, but there is no evidence that acute inflammation of the extra-articular long head of the biceps (LHB) tendon is the root cause of this condition. We evaluated the histologic findings of the extra-articular portion of the LHB tendon and synovial sheath in order to compare those findings to known histologic changes seen in other tendinopathies. Methods: Twenty-six consecutive patients (mean age 45.4±13.7 years) underwent an open subpectoral biceps tenodesis for anterior shoulder pain localized to the bicipital groove. Excised tendons were sent for histologic analysis. Specimens were graded using a semiquantitative scoring system to evaluate tenocyte morphology, the presence of ground substance, collagen bundle characteristics, and vascular changes. Results: Chronic inflammation was noted in only two of 26 specimens, and no specimen demonstrated acute inflammation. Tenocyte enlargement and proliferation, characterized by increased roundness and size of the cell and nucleus with proteoglycan matrix expansion and myxoid degenerative changes, was found in all 26 specimens. Abundant ground substance, collagen bundle changes, and increased vascularization were visualized in all samples. Conclusion: Anterior shoulder pain attributed to the biceps tendon does not appear to be due to an inflammatory process in most cases. The histologic findings of the extra-articular portion of the LHB tendon and synovial sheath are similar to the pathologic findings in de Quervain tenosynovitis at the wrist, and may be due to a chronic degenerative process similar to this and other tendinopathies of the body. Keywords: biceps tendinitis, biceps tendinopathy, tenosynovium, anterior shoulder pain, long head biceps tendon, histologic analysis

Development and implementation of a holistic method for scoring writing assignments in a college general education chemistry course are described. The system included assessment of discrete elements in the paper's focus, appearance, content, and structure according to specific criteria. The approach saved considerable scoring time and enhanced student understanding. (MSE)

DNA nanotechnology has been employed to develop devices based on i-motif structures. The protonated cytosine-cytosine base pairs that stabilize i-motif conformations are favored under slightly acidic conditions. This unique property has enabled development of the first DNA molecular motor driven by pH changes. The ability to alter the stability and pH transition range of such DNA molecular motors is desirable. Understanding how i-motif structures are influenced by modifications, and which modifications enhance stability and/or affect the pH characteristics, are therefore of great interest. Here, the influence of 5-halogenation of the cytosine nucleobases on the base pairing of protonated cytidine nucleoside analogue base pairs is examined using complementary threshold collision-induced dissociation techniques and computational methods. The nucleoside analogues examined here include the 5-halogenated forms of the canonical DNA and RNA cytidine nucleosides. Comparisons among these systems and to the analogous canonical base pairs previously examined enable the influence of 5-halogenation and the 2′-hydroxy substituent on the base pairing to be elucidated. 5-Halogenation of the cytosine nucleobases is found to enhance the strength of base pairing of DNA base pairs and generally weakens the base pairing for RNA base pairs. Trends in the strength of base pairing indicate that both inductive and polarizability effects influence the strength of base pairing. Overall, the present results suggest that 5‑halogenation, and in particular, 5-fluorination and 5-iodination, provide effective means of stabilizing DNA i-motif conformations for applications in nanotechnology, whereas only 5-iodination is effective for stabilizing RNA i-motif conformations but the enhancement in stability is less significant. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a simple biological system suitable for the treatment of dairy parlor wash waters. A novel horizontal-flow biofilm system with step feed was designed, constructed, and tested in the laboratory for organic carbon removal, nitrification, and denitrification of a synthetic dairy wastewater with average filtered chemical oxygen demand ([COD.sub.f]) of 2,060 mg/L, total nitrogen (TN) of 288 mg/L, and ammonia nitrogen ([NH.sub.4]-N) of 127 mg/L. The novel biofilm system consisted of two reactor units placed on top of one another, each comprising a stack of horizontal plastic sheets. Part of the wastewater was pumped onto Sheet 1 (top feed) and the remainder onto Sheet 11 (step feed) and flowed over the horizontal sheets down through the system. Three hydraulic loading rates were examined: 32.3, 25.1, and 19.3 L/[m.sup.2] day, based on the top plan area, and the respective removals of [COD.sub.f] were 96, 96, and 97% and of TN, 86, 83, and 75% were achieved. The system was simple and cheap to construct and operate. DOI: 10.1061/(ASCE)0733-9372(2007)133:6(569) CE Database subject headings: Agriculture; Biofilm; Biological treatment; Environmental engineering; Nitrification; Denitrification; Wastewater management.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2006.03.005 Byline: M.G. Healy, M. Rodgers, J. Mulqueen Keywords: Recirculating sand filters; Dairy parlor wastewaters; Forward flow; Organic loading rate Abstract: A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10Lm.sup.-2 d.sup.-1; a higher system hydraulic loading rate (of 13.4Lm.sup.-2 d.sup.-1) caused surface ponding. The system hydraulic loading rate of 10Lm.sup.-2 d.sup.-1 gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1gm.sup.-2 d.sup.-1, respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO.sub.3-N concentration of 42mgL.sup.-1 (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment. Author Affiliation: Department of Civil Engineering, National University of Ireland, Galway, Ireland Article History: Received 23 June 2005; Revised 21 January 2006; Accepted 15 March 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.07.003 Byline: M. Rodgers, M.G. Healy, J. Prendergast Abstract: A laboratory continuous feed biofilm reactor, comprising a bulk fluid reactor, a biofilm plastic module, a feed tank, and pneumatic devices and controls, was operated for a total period of 257 days, including seeding time, to treat domestic-strength synthetic wastewater under increasing ammonium nitrogen (NH.sub.4.sup.+-N) loading rates, ranging from 0.17[+ or -]0.01 (0.71[+ or -]0.06gm.sup.-2 d.sup.-1) to 0.70[+ or -]0.02kgm.sup.-3 d.sup.-1 (2.9[+ or -]0.1gm.sup.-2 d.sup.-1). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum NH.sub.4.sup.+-N removal rate was reached during the maximum loading phase, when a NH.sub.4.sup.+-N loading rate of 0.70[+ or -]0.02kgm.sup.-3 d.sup.-1 (2.9[+ or -]0.1gm.sup.-2 d.sup.-1) was applied to the system. During this loading period, the average NH.sub.4.sup.+-N removal rate was 0.30[+ or -]0.10kgm.sup.-3 d.sup.-1 (1.30[+ or -]0.40gm.sup.-2 d.sup.-1). Author Affiliation: Department of Civil Engineering, National University of Ireland, Galway, Ireland Article History: Received 23 December 2004; Revised 7 June 2005; Accepted 26 July 2005