Filling the gap: Calibration of the low molar-mass range of cellulose in size exclusion chromatography with cello-oligomers.

Degraded celluloses are becoming increasingly important as part of product streams coming from various biorefinery scenarios. Analysis of the molar mass distribution of such fractions is a challenge, since neither established methods for mono- or disaccharides nor common methods for polysaccharide characterization cover the intermediate oligomer range appropriately. Size exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS), the standard approach for celluloses, suffers from decreased scattering intensities in the lower-molar mass range. The limitation in the low-molecular range can, in principle, be overcome by calibration, but calibration standards for such "short" celluloses are either not readily available or structurally remote and thus questionable. In this paper, we present the calibration of a SEC system- for the first time - with monodisperse cellooligomer standards up to about 3400gmol-1. These cellooligomers are "short-chain celluloses" and can be seen as the "true" standard compounds, by contrast to commonly used standards that are chemically different from cellulose, such as pullulan, dextran, polystyrene, or poly(methyl methacrylate). The calibration is compared against those commercial standards and correction factors are calculated. Calibrations with non-cellulose standards can now be adjusted to yield better fitting results, and data already available can be corrected retrospectively.

Helicobacter pylori prevalence in Leipzig's 1998 school entries: methodology and first results.

The non-invasive, stable-isotope-aided Helicobacter pylori (H. pylori) tests--breath and equivalent urine tests--were offered on a voluntary basis as part of the mandatory school entry medical examination to the 1998 school entry cohort of the City of Leipzig (480,000 residents). Parents of participating subjects were asked to fill out a detailed epidemiologic questionnaire. The response rate was 94% (n = 2228 of 2369 school starters born in 1991/92). Parent-completed questionnaires were returned by 1890 (80%) children. The overall H. pylori positive prevalence was 7.2%. The prevalence among children with a test and a parent-completed questionnaire was 6.5%. Prevalences among subsequently tested family members of the positive tested children was 65, 60 and 39% for mothers, fathers and siblings respectively. Though studies have shown that the direct transmission of the bacterium (oral-oral and fecal-oral) is a dominant pathway of infection, the questionnaire analyses indicate associations between H. pylori colonisation and living as well as environmental conditions.

Structure-based design guides the improved efficacy of deacylation transition state analogue inhibitors of TEM-1 beta-Lactamase(,).

Transition state analogue boronic acid inhibitors mimicking the structures and interactions of good penicillin substrates for the TEM-1 beta-lactamase of Escherchia coli were designed using graphic analyses based on the enzyme's 1.7 A crystallographic structure. The synthesis of two of these transition state analogues, (1R)-1-phenylacetamido-2-(3-carboxyphenyl)ethylboronic acid (1) and (1R)-1-acetamido-2-(3-carboxy-2-hydroxyphenyl)ethylboronic acid (2), is reported. Kinetic measurements show that, as designed, compounds 1 and 2 are highly effective deacylation transition state analogue inhibitors of TEM-1 beta-lactamase, with inhibition constants of 5.9 and 13 nM, respectively. These values identify them as among the most potent competitive inhibitors yet reported for a beta-lactamase. The best inhibitor of the current series was (1R)-1-phenylacetamido-2-(3-carboxyphenyl)ethylboronic acid (1, K(I) = 5.9 nM), which resembles most closely the best known substrate of TEM-1, benzylpenicillin (penicillin G). The high-resolution crystallographic structures of these two inhibitors covalently bound to TEM-1 are also described. In addition to verifying the design features, these two structures show interesting and unanticipated changes in the active site area, including strong hydrogen bond formation, water displacement, and rearrangement of side chains. The structures provide new insights into the further design of this potent class of beta-lactamase inhibitors.

A motivational systems approach to the clinical experience.

A conception of the self and five motivational systems is applied to clinical psychoanalysis. Each motivational system develops in infancy from innate and learned patterns in response to a basic need, and each involves particular affects. Each motivational system contributes patterns from which important transferences evolve. At any given moment, motives derived from one or another system dominate a person's experience, motives from the other system being subsidiary or dormant. We describe the manner in which these concepts contribute to an explanation of foreground-background relations during analysis, and how analysts and analysands construct model scenes to give meaning to information acquired by empathic listening. We conclude with a clinical vignette illustrating the application of these concepts to the patient's transference and the analyst's response in the intersubjective realm of an analytic enactment and verbal exchange.

Effect of fat and lactose supplementation on digestion in dairy cows. 1. Nonlipid components.

Seven cows, of which five were fitted with rumen and duodenal cannulae, alternately received "milk" diet with 10% fat and 13% lactose, and control diet with 2% fat and no lactose. Both diets were 60% hay. Organic matter and crude fiber digestibilities were not different between milk diet (73.4 and 68.1%) and control diet (74.1 and 70.5%). The quantity of organic matter degraded in the rumen (percent of intake) was higher with control diet (51%) than with milk diet (44%). Ratio of duodenal nonammonia nitrogen to nitrogen intake was higher with milk diet. Both diets gave the same rumen pH. The milk diet increased butyrate and minor volatile fatty acids and decreased acetate proportions. The milk diet increased plasma beta-hydroxybutyrate and decreased plasma acetate. These differences were significant only after feeding. Changes in the characteristics of digestion with milk diet were related more to lactose than to fat. No decrease in fiber digestion was seen with the milk diet despite its high fat content.

Effect of fat and lactose supplementation on digestion in dairy cows. 2. Long-chain fatty acids.

Dairy cows fitted with rumen and proximal duodenal cannulae were given diets of 60% hay, 7% soybean and rapeseed meal, and either 33% concentrate (control diet) or 33% milk (lipid-supplemented diet: "milk" diet). Amounts of total long-chain fatty acids consumed, entering the duodenum and excreted in the feces were examined. Long-chain fatty acid intake was 192 and 764 g/d with the control and milk diets, respectively. The duodenal flow of long-chain fatty acids was greater (17.3%) than the amount consumed when the control diet was fed; with the milk diet, there was a net loss (-22.2%), mainly due to a decrease in total C16 and C18 acids. The extent of C18:2 hydrogenation in the rumen was reduced by the high fat ration, but for C18:3, hydrogenation was very high and unchanged. Apparent intestinal digestibility of fatty acids was high, especially on the milk diet (86.1%), although the amount of fatty acids absorbed (60.6 g/kg dry matter intake/d) was three times greater than with the control.

Characterization of glycosaminoglycans stored in mucopolysaccharidosis III A: evidence for a generally occuring degradation of heparan sulfate by endoglycosidases.

The characterization of intracellularly stored glycosaminoglycans from organs of a patient suffering from mucopolysaccharidosis III A (Sanfilippo A disease) is described. Both heparan sulfate and galactosamine-containing glycosaminoglycans (chondroitin sulfate, dermatan sulfate) are accumulated in the liver, whereas in the other organs (spleen, kidney, heart, cerebrum, cerebellum) heparan sulfate is almost the only glycosaminoglycan stored. It is shown by [3H]NaBH4 reduction and subsequent identification of the 3H-labelled sugar alcohols that heparan sulfate is degraded in all organs by at least two endoglycosidases, an endoglucuronidase and an endoglucosaminidase, to fragments of low molecular weight (Mr approximately 2 000-6 600).