AJUR Volume 18 Issue 1 (June 2021)



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Links to individual manuscripts, abstracts, and keywords are provided below.

p3. Enzymatic and Structural Characterization of Alanine Racemase from Enterococcus faecium by Kinetic and Computational Studies
Arie Van Wieren*, Emma Bouchard, & Sudipta Majumdar
ABSTRACT: The surge in vancomycin-resistant enterococci (VRE)strains poses a serious threat to public and clinical health. VRE strains are the leading cause of multi-drug resistant enterococcal infections and are commonly acquired from medical devices. Therefore, it is essential to discover new antibacterial targets and drugs for this pathogen. Alanine racemase could be a valuable drug target due to its crucial role in E. faecium survival. Alr from E. faecium (EF_Alr) was heterologously produced and purified from E. coli., and the steady-state kinetic constants were determined at different pH values. Using a coupled reaction with L-alanine dehydrogenase, rate of production of NADH was measured at 340 nm to observe EF_Alr activity in the D- to L-alanine direction. The highest catalytic efficiency, 8.61 ± 0.5 s-1 mM-1, was found at pH 9. Additionally, the tentative active site residues, Lys40 and Tyr268, for the alanine racemization reaction were assigned by homology modeling and sequence comparison studies. Using UCSF Chimera, the structure of the EF_Alr homology model was superimposed and compared to the crystal structure of Alr from E. faecalis.
KEYWORDS: Alanine Racemase; Enterococcus faecium; Vancomycin-Resistant Enterococci; Homology Modeling; pH Optimum; Kinetic Characterization; SWISS-MODEL Server; Steady-State Kinetics

p.13 Is Play Sexually Dimorphic in the Polygamous Squirrel Monkey?
Seta Aghababian, Anita Stone, & Christopher Brown
ABSTRACT: Play behavior is widespread in juvenile mammals and may be a mechanism for practicing skills needed in adulthood. In mammals characterized by strong adult male competition over females, juvenile males perform more social play than do females, and such play may assist in later mating competition. This study examined whether social play behavior is sexually dimorphic in a polygamous neotropical primate, the squirrel monkey (Saimiri collinsi), through a six-week field study of two groups of wild monkeys in Eastern Amazonia, Brazil. We hypothesized that males would conduct more rough-and-tumble play than females and that any sex-based play differences would be more evident in older juveniles. We video recorded juvenile play bouts and scored: age category (younger or older juvenile) and sex of players (male or female); and rough-and-tumble play behaviors (i.e., bite, grab, and wrestle). Juvenile males initiated more play bouts than did females. Most players were older juvenile males, while older juvenile females were the least represented. Older juvenile play bouts occurred mostly among males, while younger juvenile bouts consisted of a more even sex distribution. While younger juveniles did not significantly affect the number of rough-and-tumble behaviors in bouts, the number of behaviors was significantly affected by the sex of older individuals. These results indicate that social play is sexually dimorphic in juvenile S. collinsi; specifically, males play more than females and sex differences are more pronounced in older cohorts.
KEYWORDS: Squirrel Monkeys; Mating System; Sexual Dimorphism; Juvenile Period; Development; Play Behavior; Social Behavior; Ethology