No description available.

No description available.

Suspensions of C. perfringens, when grown on a peptone-free, semi-defined medium, have been shown to remain resistant to autolysis for extended periods of time. The stability of these suspensions has been compared with that of cells grown on complex media. Extracts of cells grown on this semi-defined medium were found to contain all of the enzymes of the Embden-Meyerhof pathway of glycolysis, in addition to lactic acid dehydrogenase and the pyruvate-clastic system, but no evidence of glucose-6-phosphate dehydrogenase activity could be demonstrated. Evidence has been presented for the implication of the Embden-Meyerhof pathway as the major pathway of glucose degradation by this organism. Resting suspensions of C. perfringens were shown to transport radioactive glucose and mannose, but not other carbohydrates by a common mechanism and accumulate glucose to concentrations several hundred times those found in the external medium. The transport system was found to be an enzymatic, energy-dependent, temperature-sensitive, and highly specific mechanism which was saturated at high substrate concentrations. The carbohydrate was found to be accumulated as an equilibrium mixture of phosphorylated hexoses. The phosphorylation mechanism involved in accumulation was demonstrated to be other than the soluble hexo-kinase. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

Thesis advisor: Marc L. Snapper / This dissertation will present four main projects that I have been working on since January 2015. The first two chapters will be focusing on the developments of the carbohydrate-catalyzed enantioselective alkene diboraiton. The exchange catalysis between carbohydrate-derived diol catalyst and diboron starting material renders the alkene diboration reaction possible without the aid from transition metals. This successfully brought down the cost for the enantioselective alkene diboration, making it an appealing tool for alkene transformation. Detailed mechanistic study that leads to the reaction efficiency improvements were discussed in chapter 2. The third chapter of this dissertation is about the developments of site-selective oxidation of 1,2-bis(boronate). This is a new type of a reaction motif that the alkene diboration product can undergo. The secondary boronic ester of the 1,2-bis(boronate) was selectively oxidized to hydroxyl group while leaving the primary boronic ester untouched. This new reaction opens up a variety of opportunities to transform 1,2-bis(boronate) into different functional groups. Lastly, in the fourth chapter, recent synthetic methods developed in the Morken group was used in the total synthesis study of complex natural product Amphidinolide C. As it is disclosed, the carbohydrate-catalyzed enantioselective alkene diboration proved to be a powerful transformation either in early stage starting material preparation or in late stage complex structure motif functionalization. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

In this study, we investigated the potential applications of carbohydrates in the development of new antibiotics. To tackle the problem of multidrug-resistant variants of M. tuberculosis (MDR-TB), we investigated the biosynthesis pathways of trehalose, which has contributed to significant drug resistance. Some new methods were developed for the synthesis of potential inhibitors (6-azido-trehalose and 6,6'-diazido-trehalose) that have been designed to imitate the intermediate molecule (trehalose 6-phosphate, TPP) of OtsA-OtsB pathway. At the same time, some new antibacterial agents based on trehalose have been synthesized. Members of the 1,2,3-triazole family have shown interesting biological properties. Steroid derivatives have been developed in antibiotics area. Therefore click reaction was utilized to build a 1,2,3-triazole ring and combine cholesterol with different carbohydrate moieties. A series of new compounds has been synthesized and their bioactivities have been tested.

This study was designed to investigate carbohydrate supplementation during cheerleading training and its effect on performance. Seventeen participants in four trials; one to gather anthropometric data and 1-repetition maximums, one familiarization trial, a carbohydrate trial, and a placebo trial. The exercises used were power snatches from a hang position, push jerks, front squats, and box squats. The exercises most mimicked a standard strength and conditioning practice for cheerleaders. Performance was measured by calculating the difference between pre- and post-training values in vertical jump repetitions, peak power, average power, peak velocity, and average velocity in a power snatch, and a 200-m shuttle sprint. Performance values for carbohydrate and placebo trials were analyzed using a paired sample t-test, which found no significant difference between the carbohydrate and placebo trials.

No description available.

No description available.

Cyanobacteria of the Nostoc genus are known for the thick, mucilaginous carbohydrate coatings that they produce. In this work, two examples of cyanobacterial glycobiology are considered, each of which involves a cyanobacterium of the Nostoc genus. The first portion of this work details attempts to obtain amino acid sequence information from the enzymes (glycosyltransferases) that are responsible for producing the extracellular polysaccharide (EPS) of Nostoc commune DRH1, ultimately to allow the transfer of this capacity to another organism. Two artificial substrates were synthesized for use in a capillary electrophoresis-based enzyme assay, which was used to look for glycosyltransferase activity in Nostoc commune DRH1 cell extracts. Glucuronosyltransferase activity was detected in association with Nostoc commune membrane material. The active enzyme displayed a divalent cation metal dependence (Mg+2) that is typical of glycosyltransferase enzymes purified from other organisms. Because the enzyme responsible for this activity held the potential to be EPS-related, its purification was attempted. The capillary electrophoresis-based enzyme assay and a 32P-labeled affinity tag were utilized to follow the glucuronosyltransferase enzyme through successive purification steps. The active enzyme was extracted from Nostoc commune membrane material using Triton X-100, and then purified by anion exchange chromatography. The active detergent extract was extremely unstable, and consequently, other purification techniques tested were unsuccessful in enriching activity. Affinity-labeling experiments indicated that the active enzyme was forming protein aggregates during these procedures, which were not amenable to in-gel protease digestion and peptide analysis by tandem mass spectrometry. The second portion of this work describes an investigation of an Anabaena (Nostoc) PCC 7120 soluble cell extract. Upon separation by sodium dodecyl sulfate ¡V polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent periodic acid-Schiff (PAS) staining of the resulting gel, the components of this cellular fraction produce a ladder-like pattern, which suggests that the extract may contain glycosylated protein. Analyses of several samples that were taken from within the PAS-staining region of such a gel revealed surface layer homology (SLH) domain-containing proteins, likely candidates to be covalently attached to or non-covalently interacting with carbohydrate. Various protein sequence analyses indicated that the detected SLH domain containing proteins belong to a family of (putative) cyanobacterial porins. Proteins in this family possess features that include a N-terminal signal sequence, a single SLH domain motif, followed by a coiled-coil region, and a C-terminal region that is homologous to the b-barrel-forming region of bacterial porins. All of these features were identified in the detected Anabaena (Nostoc) PCC 7120 SLH domain-containing proteins. Smith degradation was performed on a sample that was electroeluted from the PAS-staining region of a preparative-scale SDS-PAGE gel of the soluble cell extract. Subsequent analyses of the resulting sample by SDS-PAGE and mass spectrometry indicated that at least two SLH domain-containing proteins, encoded by all4499 and alr4550, were non-covalently interacting with the PAS-staining material. Following degradation, the PAS-staining material was still of sufficient size to detected by gel electrophoresis, and it continued to migrate in the absence of an interacting protein component. Protease digestion of a similarly prepared sample, and then subsequent analysis by SDS-PAGE and mass spectrometry, revealed that the region between amino acid residues #504 and #536, in the protein encoded by the alr4550 open reading frame, was interacting with the PAS-staining material. Monosaccharide composition analyses of this material revealed more carbohydrate constituents than are found in cyanobacterial primary (peptidoglycan) cell wall polymer alone, indicating that it contained a significant secondary cell wall polymer component as well. / Ph. D.

The controversial condition of carbohydrate craving is believed by some researchers to be a defect in the regulation of food intake by an individual. This defect is believed to be responsible for the inability of some persons to control their food intake and therefore their weight. Research was conducted to test the hypothesis that, given a group of carbohydrate cravers and a group of noncravers, the cravers will experience a greater plasma insulin response (concentration and area under the curve) than will the noncravers, and that, because of this higher response, the cravers will experience equal or lower plasma glucose levels during a carbohydrate load. A second hypothesis was that, because of cephalic insulin response due to sensory stimuli, cookies would elicit a greater plasma insulin response than would a glucose solution. This higher plasma insulin response may in part explain the uncontrollable snacking that some individuals experience. The purpose of this research was to attempt to identify a biochemical distinction between persons who crave carbohydrates and persons who do not crave carbohydrates. Eleven overweight female subjects, age 30 to 40, were recruited and divided into two groups, five carbohydrate cravers and six noncravers, based on scores received on a questionnaire that was devised for this study to attempt to distinguish between the groups. A Restrained Eating questionnaire was also administered to the subjects. Both groups had similar, but high, restrained eating scores, indicating that all of the subjects were probably restrained eaters. The eating restraint, as supported by the reported frequency of dieting among the subjects, may well have influenced the subjects' responses to the carbohydrate craving questionnaire. Utilizing these two groups of subjects, two tests were administered. The oral glucose tolerance test was administered, utilizing 75 g of carbohydrate each in the forms of glucose solution and cookies, which were administered in a random order. The tests were administered during the premenstrual phase of the subjects' menstrual cycles, 0-10 days prior to the onset of menstruation. Blood was drawn and assayed for plasma glucose and insulin. The research showed that the cravers experienced a significantly greater plasma insulin concentration and area under the curve than the noncravers, particularly at the 30, 60 and 120 minute time points with the glucose treatment. For the glucose treatment, the cravers experienced plasma insulin concentrations that were 32% to 50% greater than those of the noncravers in the early portion of the test. This supports the hypothesis which states that cravers will experience a greater plasma insulin response to a carbohydrate load than will noncravers. This elevated plasma insulin level may be responsible for the carbohydrate cravings that the individuals experience. There was no significant difference in plasma glucose levels at any time point in either of the tests as compared between the cravers and noncravers, thus supporting the expectation that these levels would be similar between the groups. The hypothesis that cookies would elicit a greater plasma insulin response than would a glucose solution was not supported. Any cephalic insulin response which may have resulted from the sight and smell of the cookies, while not specifically measured, was not strong enough to override the physiological factors that control insulin release. Therefore, the glucose solution elicited a significantly greater plasma insulin concentration than did the cookies in the cravers during the first two hours of the tests, and a significantly greater area under the curve for the cravers at 60 minutes and both groups at 120 minutes. However, the cookies did have an effect on insulin release at the fasting point, causing elevated (x = 79%) plasma insulin levels in three of five subjects who were waiting while others were eating the cookies, as compared with these subjects' fasting insulin levels when they were not exposed to the cookies prior to their glucose test. Another finding was a difference between the groups in fasting plasma insulin concentrations over the 10 day premenstrual portion of their menstrual cycles. The noncravers experienced fasting plasma insulin concentrations that decreased as the onset of menstruation was approached, which would parallel the decrease in progesterone levels. However, the cravers experienced first a decrease in fasting plasma insulin levels to day 3 premenstrual, and then an increase to the level of that found 8-10 day premenstrual. This pattern is contrary to what would be expected as progesterone levels drop, and suggests an altered pattern of progesterone levels in the cravers, although progesterone was not measured in this study. To summarize, in a group of overweight women, carbohydrate cravers and non cravers, the cravers experienced a greater plasma insulin response than did the noncravers for the glucose treatment but not for the cookie treatment, and there was no significant difference between the groups for plasma glucose concentration for either treatment. / Graduation date: 1991