Transesterification of a Tertiary Alcohol by Engineered Candida antarctica Lipase†A.

Tertiary alcohols are known to be challenging substrates for applications in asymmetric synthesis due to their complexity and steric hinderance. The occurrence of tertiary alcohols and their esters in nature indicates the presence of natural biocatalytic synthetic routes for their preparation. Lipase A from Candida antarctica (CalA) is a hydrolase that has previously been shown to catalyze the transesterification of racemic 2-phenylbut-3-yn-2-ol at a low rate. In this work, the activity of that enzyme was improved by protein engineering through a semi-rational design strategy. An enzyme library was created and screened for transesterification activity towards racemic 2-phenylbut-3-yn-2-ol in an organic solvent. One successful enzyme variant (L367G) showed a tenfold increased reaction rate compared to the wild-type enzyme, while maintaining a high enantioselectivity.

Synthesis and biology of oligoethylene glycol linked naphthoxylosides.

Proteoglycans (PGs) are important macromolecules in mammalian cells, consisting of a core protein substituted with carbohydrate chains, known as glycosaminoglycans (GAGs). Simple xylosides carrying hydrophobic aglycons can enter cells and act as primers for GAG chain synthesis, independent of the core protein. Previously it has been shown that aromatic aglycons can be separated from the sugar residue by short linkers without affecting the GAG priming ability. To further investigate the effects of the xylose-aglycon distance on the GAG priming ability, we have synthesized xyloside derivatives with 2-naphthyl and 2-(6-hydroxynaphthyl) moieties connected to xylose, directly, via a methylene bridge, or with oligoethylene glycol linkers of three different lengths. The GAG priming ability and the antiproliferative activity of the xylosides, as well as the composition of the xyloside-primed GAG chains were investigated in a matched pair of human breast fibroblasts and human breast carcinoma cells. An increase of the xylose-aglycon distance from 0.24 to 0.37 nm resulted in an increased GAG priming ability in both cell lines. Further increase of the xylose-aglycon distance did not result in any pronounced effects. We speculate that by increasing the xylose-aglycon distance, and thereby the surface area of the xyloside, to a certain level would make it more accessible for enzymes involved in the GAG synthesis. The compositions of the primed GAG chains varied with different xylosides, independent of the xylose-aglycon distance, probably due to various affinities for enzymes and/or different cellular uptake. Furthermore, no correlations between the antiproliferative activities, the xylose-aglycon distances, and the amounts or compositions of the GAG chains were detected suggesting involvement of other factors such as fine structure of the GAG chains, effects on endogenous PG synthesis, or other unknown factors for the antiproliferative activity.

The perspectives of in-school youths in Kampala, Uganda, on the role of parents in HIV prevention.

This qualitative study explores how young Ugandans perceive and experience the role of parents in preventing the spread of HIV among youths. Data were gathered from semi-structured face-to-face interviews with 16 in-school youths, ages 18-20, residing in Kampala. A key finding is that the youths perceived parenting styles as influencing HIV prevention among youths. The participants identified several harmful consequences from a lack of parental guidance or inadequate parenting and they discussed the gains of parental support in terms of assisting HIV prevention among youths. The participants expressed the idea that parents can importantly contribute to preventing the spread of HIV among youths by supporting their own adolescent children and discussing topics like sex, relationships, and HIV in an age-appropriate way. However, the participants also felt that Ugandan parents in general are unable to support and talk to youths about sex and HIV in a way that helps protect them from exposure to HIV. The in-school youths felt that parents are unsupportive in terms of HIV prevention among youths by way of fear of talking about sex, parents' lack of time to engage with their children, and authoritarian or indulgent parenting. The participants also described how parents treat girls and boys differently; however, no significant association was found between how girls and boys conceptualised parents' roles.