Improved high-performance liquid chromatographic separation of peptidoglycan isolated from various Staphylococcus aureus strains for mass spectrometric characterization

Reversed-phase high-performance liquid chromatography (RP-HPLC) of muropeptides, obtained by muramidase digestion of peptidoglycan in combination with amino acid analysis and plasma desorption time-of-flight mass spectrometry is today by far the best tool to analyze the fine structure of the peptidoglycans. Here we report further improvements of the RP-HPLC separation of muropeptides for analyzing the peptidoglycans of various methicillin-resistant strains of Staphylococcus aureus, with emphasis on a more detailed characterization of the interpeptide bridge of the peptidoglycans of this species.     

Near infrared spectroscopy in fermentation and quality control for amino acid production

The application of near infrared spectroscopy (NIRS) for in-process and quality control of fermentative production of L-lysine and L-threonine in industrial scale is presented. NIRS is a helpful tool for predicting optical density, ammonia, L-threonine and L-lysine in fermentation broth. For dry and solid product, Biolys^®60, NIRS is suitable to give a quick estimation of L-lysine and water content.     

Leak measurements in spontaneously breathing premature newborns by using the flow-through technique

A new method for measuring and correcting airleaks during lung-function testing in infants has been validated invitro and in vivo by using a flow-through system that measured theinflow and outflow of a face mask. An adjustable leak was quantified byusing suction flow to validate the accuracy of leak measurements. Tovalidate the leak correction, the volume of a pump was measured withdifferent air leaks (0-30%). The method developed was tested in67 infants breathing spontaneously. There was good agreement betweenmeasured and simulated leaks (r = 0.998, P < 0.001; 95% limits ofagreement were 0.3 and 0.1%, respectively). The volume wasgenerally underestimated because of leaks, and the volume error was upto 94% compared with the maximum error of 5% after leak correction.With continuous leak measurements in vivo, there were <4% actualleaks (median 2.6%), and we did not observe any leaks in >7% ofcases. The leak correction improved the accuracy of ventilatorymeasurements. The monitoring of leaks is helpful for airtight placementof the face mask and for prevention of serious measurement errorscaused by leaks.

     

Highly processive motility is not a general feature of the kinesins

Evidence is presented that the kinesin-related ncd protein is not as processive as kinesin. In low surface density motility experiments, a dimeric ncd fusion protein behaved mechanistically more similar to non-processive myosins than to the highly processive kinesin. First, there was a critical microtubule length for motility; only microtubules longer than this critical length moved in low density ncd surfaces, which suggested that multiple ncd proteins must cooperate to move microtubules in the surface assay. Under similar conditions, native kinesin demonstrated no critical microtubule length, consistent with the behavior of a highly processive motor. Second, addition of methylcellulose to decrease microtubule diffusion decreased the critical microtubule length for motility. Also, the rates of microtubule motility were microtubule length dependent in methylcellulose; short microtubules, that interacted with fewer ncd proteins, moved more slowly than long microtubules that interacted with more ncd proteins. In contrast, short microtubules, that interacted with one or a few kinesin proteins, moved on average slightly faster than long microtubules that interacted with multiple kinesins. We conclude that a degree of processivity as high as that of kinesin, where a single dimer can move over distances on the order of one micrometer, may not be a general mechanistic feature of the kinesin superfamily. Received: 16 September 1997 / Accepted: 4 November 1997     

The consequences of partially directed search effort

Search effort is undirected when a forager has a stereotypical searching behaviour that results in fixed encounter rates with its prey (e.g. diet choice models), and is directed when the forager can bias its encounter with a ‘chosen’ prey. If the bias is complete, search is totally directed (e.g. habitat selection models). When the bias is incomplete (i.e. search modes are not exclusive to a single prey type), search is partially directed. The inclusion of a prey type in the diet is then the result of two decisions: (1) which prey to search for and (2) which prey to handle. The latter decision is determined by the ratio of energy to handling time and the abundance of the preferred prey. The former decision is a function of the encounter probabilities and densities of all potential prey types in addition to their ratio of energy to handling time. Assuming two prey types, there are three distinct behavioural strategies: (1) search for the preferred prey/forage selectively; (2) search for the preferred prey/forage opportunistically; and (3) search for the non-preferred prey/forage opportunistically. If prey are depletable (i.e. prey occur in resource patches), the forager may switch search modes such that prey are depleted to the point where the marginal values of the search modes are equalized. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatio-temporal modelling of the first Chikungunya epidemic in an intra-urban setting: The role of socioeconomic status,environment and temperature

Three key elements are the drivers of Aedes-borne disease: mosquito infestation, virus circulating, and susceptible human population. However, information on these aspects is not easily available in low- and middle-income countries. We analysed data on factors that influence one or more of those elements to study the first chikungunya epidemic in Rio de Janeiro city in 2016. Using spatio-temporal models, under the Bayesian framework, we estimated the association of those factors with chikungunya reported cases by neighbourhood and week. To estimate the minimum temperature effect in a non-linear fashion, we used a transfer function considering an instantaneous effect and propagation of a proportion of such effect to future times. The sociodevelopment index and the proportion of green areas (areas with agriculture, swamps and shoals, tree and shrub cover, and woody-grass cover) were included in the model with time-varying coefficients, allowing us to explore how their associations with the number of cases change throughout the epidemic. There were 13627 chikungunya cases in the study period. The sociodevelopment index presented the strongest association, inversely related to the risk of cases. Such association was more pronounced in the first weeks, indicating that socioeconomically vulnerable neighbourhoods were affected first and hardest by the epidemic. The proportion of green areas effect was null for most weeks. The temperature was directly associated with the risk of chikungunya for most neighbourhoods, with different decaying patterns. The temperature effect persisted longer where the epidemic was concentrated. In such locations, interventions should be designed to be continuous and to work in the long term. We observed that the role of the covariates changes over time. Therefore, time-varying coefficients should be widely incorporated when modelling Aedes-borne diseases. Our model contributed to the understanding of the spatio-temporal dynamics of an urban Aedes-borne disease introduction in a tropical metropolitan city.