A detailed understanding of the mechanism of organic cocrystal formation remains elusive. Techniques that interrogate a reacting system in situ are preferred, though experimentally challenging. We report here the results of a solid-state in situ NMR study of the spontaneous formation of a cocrystal between a pharmaceutical mimic (caffeine) and a coformer (malonic acid). Using (13)C magic angle spinning NMR, we show that the formation of the cocrystal may be tracked in real time. We find no direct evidence for a short-lived, chemical shift-resolved amorphous solid intermediate. However, changes in the line width and line center of the malonic acid methylene resonance, in the course of the reaction, provide subtle clues to the mode of mass transfer that underlies cocrystal formation.
Biofilms form when planktonic, or freely swimming, bacteria adhere to a surface. Once adhered, connections form with other bacteria through extracellular polymeric substances (EPS). Biofilms can form on medical devices, causing persistent infections in patients, and on industrial equipment, which is known as biofouling. Biofilms present a unique challenge, as they can exhibit a higher tolerance for antibiotics than their planktonic counterparts. Curli are extracellular quaternary protein structures associated with robust biofilm formation in E. coli. They have been shown to aid in initial adhesion of the bacterial cells to a surface.Here, we induced the overexpression of rpoF, also known as fliA and σ28, which codes for a flagellar transcription factor important in late‐stage flagellar assembly, in PHL628 E. coli, which overexpress curli at growth temperatures less than 30 °C. Because rpoF increases cell motility, we originally predicted that rpoF overexpression would decrease the amount of biofilm formation. However, we observed that rpoFoverexpression increased the amount of biofilm formed. We now suspect that the nature of rpoF overexpression's effects on biofilm formation may be through changing the composition of the EPS. To test this hypothesis, we grew biofilm under different conditions, and then analyzed the biomolecule composition of the EPS, as well as the overall biofilm volume using confocal laser scanning microscopy (CLSM). We used the dyes Thioflavin T and Calcofluor White to quantify extracellular amyloid proteins and carbohydrates, respectively. We found that rpoF overexpression increases the amount of extracellular carbohydrates. We also observed more curli formation when rpoF was overexpressed at lower temperatures, but not at higher growth temperatures. This suggests that curli does not account for increased biofilm formation at higher temperatures. In future experiments, we will continue similar imaging and analysis methods with Sypro Ruby (extracellular protein concentration), propidium iodide (eDNA), and DiD’ oil (lipid concentration) to obtain a more complete picture of how rpoF changes the composition of the biofilm EPS.
Pulse consumption can prevent obesity in rodents challenged with high levels of dietary fat. In the C57BL/6J mouse, high fat diets also have been shown to reduce mammary ductal development. In this study, we hypothesized that dietary lentils would prevent the increased adiposity and diminished mammary ductal development that occurs in high fat‐fed C57BL/6J mice. Female mice (5/treatment) were fed either Harlan‐Teklad 2020x (2020x, 6.5% fat), Harlan TD.88137 (HF, 21% fat, 34% sucrose), or Harlan TD.88137 with cooked, freeze‐dried lentils added at 15% (HFL). After 4 weeks on the diets, females fed HFL had higher (P<0.05) weight gain than both 2020x and HF. However, body fat mass and percent fat were similar among 2020x and HFL, and both lower (P<0.05) than that of HF females. In addition, wet weight of both the parametrial and mammary fat pads were similar among 2020x and HFL, and lower in weight (P<0.05) than HF females. Comparison of mammary ductal morphometry measurements revealed only modest dietary effects. These data demonstrate that dietary lentils can counteract the increased body fatness effect of a high fat diet in growing female mice. Grant Funding Source: Supported by The American Pulse Association
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