Prokaryotic cyanobacteria have been studied as the simplest organisms that exhibit circadian rhythms. The central S.elongatus clock is comprised of at least three components, the proteins KaiA, KaiB and KaiC. The phosphorylation status of KaiC can sustain a ca. 24-hour period in vitro with the presence of the two other Kai proteins and ATP. Synchronization of different oscillators can be achieved by mixing two KaiABC in vitro samples that are in different phosphorylation phases, with prior results indicating that their rhythms continue, yet with a synchronized shared phase. I have focused on investigating the synchronization of oscillators with different periods in vivo and in vitro with the goal of elucidating the underlying mechanisms. Interdisciplinary approaches including molecular biology, biochemistry and computational simulation are combined to demonstrate that co-existence of two oscillators with different periods displays a robustly synchronized rhythm with an intermediate period both in vivo and in vitro. Moreover, the computationally simulated results agree with the in vitro experiment, and imply that monomer exchange may work together with KaiA sequestration to secure the molecular synchronization of KaiC population in the in vitro reaction.

One commonly cited mechanism for the success of invasive species is their superior competitive ability relative to that of native species. Although 88% (22 of 25) of the empirical studies support the prediction that the strength of competition for native species increases with latitude, no studies to date have compared the competitive ability of native and co-occurring invasive species across a broad latitudinal range. In a greenhouse, I investigated whether the competitive ability of North American native and European invasive haplotypes of Phragmites australis vary with latitude. Another widespread, non-indigenous haplotype, the Gulf Coast haplotype, was also included for assessment of competitive ability only. Competitive ability of each haplotype was evaluated against a standardized plant species, Spartina alterniflora, which is a common co-inhabitant of coastal marshes. The competitive ability (measured in terms of the proportional reduction in biomass of plants grown in the presence and absence of a potential competitor) of native haplotypes decreased with increasing latitude, whereas the competitive ability of invasive haplotypes showed no relationship with latitude. This study provided the first evidence that native and invasive species (or haplotypes) exhibit non-parallel gradients in competitive ability. Overall, the invasive haplotype was competitively superior to the native haplotype - biomass production of S. alterniflora was 19% lower when grown with the former than the latter haplotype. Moreover, in the presence of an interspecific competitor, the invasive haplotype produced 45% more aboveground biomass and 50% more belowground biomass than the native haplotype. Results also indicated that the Gulf Coast haplotype was not significantly different from either the native or invasive haplotypes in terms of competitive ability. Because the invasive haplotype appeared to have the greatest competitive advantage over the natives at northern latitudes, it may be more successful in this region of its invaded range. The results from this research indicate that novel and important findings are possible when the mechanisms concerning invasion success, such as biotic resistance and competition, are examined from a biogeographical perspective.

Evidence suggests that 15-lipoxygenase-2 (15-LOX-2) plays an important role in the progression of atherosclerosis. Due to the medical need to discover isoform specific inhibitors of 15-LOX-2, a novel human enzyme, our goal was to determine the 3-dimensional structure. Using bacterial expression, we were able to obtain a usable quantity of enzyme with a sufficient amount of the catalytic iron bound to the enzyme, however it was sensitive to cleavage by proteases. This led to a ratio of roughly 1:1 of cleaved and uncleaved protein after the final step of purification. Solving the crystal structure revealed the reason for the protease sensitivity. In the polycistin-1 lipoxygenase alpha-toxin (PLAT) domain of the protein there is a large loop composed of nonpolar amino acids, which is flanked by calcium ions. The next step was to determine the purpose of calcium binding. Analytical size exclusion chromatography (SEC) experiments revealed that when calcium binding sites were mutated, the enzyme could not bind the synthetic phospholipid bilayer mimic, nanodiscs, which indicated that calcium is necessary for membrane binding. In the crystal structure, the active site of 15-LOX-2 contained a detergent molecule, C8E4, which was necessary for crystallization. This detergent molecule was later identified as a competitive inhibitor and its size and flexibility make it comparable to the enzymes natural substrate arachidonic acid (AA). Comparison of the structure of 15-LOX-2 with the stable 5-LOX structure suggested that the 5-LOX active site is occluded by the broken α2-helix and must open for substrate acquisition. This structure will provide information relevant to the design of isoform specific inhibitors which will aid in determining the function of 15-LOX-2 and could result in the development of therapeutic agents to protect against atherosclerotic plaque development.

This study was undertaken to test whether frequent quizzing would have different learning outcomes with the different populations within the classroom. Normalized mean learning gains were compared among classes that were quizzed or not quizzed. Allied Health Honors, Allied Health Academic and Academic classes in a high school biology classroom were given pre- and posttests in three units of study: protein synthesis, genetics, and classification. The same student population was also analyzed based on academic achievement levels: high, medium and low. In each unit, the experimental group was taught with traditional power point based lectures and guided notes, laboratories, activities, frequent questioning, and post-lecture quizzes. The control group was instructed with the same methods but did not complete the post-lecture quizzes but was allowed independent study time in the classroom to account for class time when the experimental group was quizzing. Pretest, posttest, learning gains, and effect size were calculated across each class type and achievement level. All quizzed populations had a higher normalized learning gain than their non-quizzed counterparts in every unit. Even though the differences were not always statistically different, the student populations were positively affected by frequent quizzing. Frequent quizzing is an effective tool to increase learning in student populations in general, despite any differences in motivation or achievement. Further study with more groups of students may lead to a better understanding of how frequent quizzing impacts the learning of different student populations.

The purpose of this study was to determine if students learn more from completing web based homework (WBHW) compared to completing homework by traditional means with pen and paper. Determining the efficacy of WBHW is important because many schools are being pressured to implement technology in the classroom. To determine the effectiveness of WBHW, student normalized learning gains were calculated from pre and post-test scores for 62 students. Learning gains were then compared when students completed WBHW, traditional homework, or did not complete homework at all, over four units in a high school chemistry class. No difference in learning gains were observed between the students completing traditional homework and those completing electronic homework. However, those students that completed either type of homework had significantly higher learning gains than those that did not complete their homework. Students were more likely to complete their homework when assigned on paper (86.7% of students) than on the computer (64.4% of students). Students also self-reported a preference for paper homework to WBHW. For example, 66% of students reported good or great learning gains as a result of traditional homework, compared to only 10% of students reporting the same for WBHW. The results of this study, demonstrate the importance of educators assigning meaningful homework in a method that students are likely to complete. High school chemistry students showed a preference toward traditional methods but, either method of homework completion was related to positive learning gains for students.

Every student has a different mindset, or their own way of viewing challenges and setbacks. The purpose of this study was to determine the effectiveness of a specific feedback intervention on student mindset and achievement in a middle school life science course. Several tests were used to compare the data at the beginning of the school year and at the end of the school year. These tests included mindset, competency in science, attitudes about learning science, and life science content knowledge. The control group was taught by the use of lecture, note-taking, and life science activities. The experimental group was taught using the same instruction, and in addition the students participated in a mindset intervention involving specific, constructive feedback. The intervention was termed growth conferences. There were no significant differences in the pre versus post scores for mindset, competency in science, or attitude towards science. These data suggest that utilizing individual growth conferences for one semester in a middle school life science setting was not effective for creating significant changes in mindset, competency in science, attitude towards science, or life science content knowledge. The control groups GPA did decrease significantly from sixth to seventh grade, while the experimental groups GPA remained the same from sixth to seventh grade. When the gifted class data was removed from the control groups GPA there was not a significant difference from sixth to seventh grade. This indicated that the students in the control group, mainly the gifted students, needed a mindset intervention, and that the mindset intervention may have prevented the experimental groups GPA from decreasing over the year. There were also data to support that as mindset increased, so did life science content knowledge and performance. If the present study were to be repeated the intervention should be more frequent, perhaps a weekly group intervention, instead of individual conferences. This would allow for the students to experience the intervention for more time throughout one semester or a school year.

Self-regulation and self-efficacy are both necessary for students to be independent learners. During middle school, students begin to yearn for academic autonomy, but lack the ability to regulate themselves and are unreasonable about their abilities. Goals have been proven to promote the development of these two skills. The purpose of this investigation was to determine which type of performance goal most efficiently promotes the development of self-regulation. The effects of performance goal source were analyzed to determine if teacher-assigned or student assigned performance goals produce greater growth in content knowledge for seventh grade life science students. The effects of goal source on goal attainment, test-anxiety, and goal orientation were also measured. Goal source did have a significant effect on normalized learning gains (nLGs). Students with teacher-set goals consistently had higher nLGs compared to students with self-assigned goals, these differences being significant for two units. It was also found that teacher-assigned performance goals produce greater nLGs amongst white students and female students. For all four units, a positive correlation between unit goals and nLGs could be found for students with teacher-set goals, indicating that assigning students higher assigned goals produces greater gains. This relationship could not be established for students with self-assigned goals. The mean goal set by the teacher was significantly lower than the mean student-set goal for three units. In the final unit, the mean goal for both groups were not statistically different, indicating that students were beginning to grasp the concept of what is a realistic goal. Both groups experienced an increase in goal attainment over the course of study, however the rate of attainment was greater for students with teacher-set goals. Test anxiety did not significantly increase over the course of the study. An inverse relationship between test anxiety and nLGs was initially established for students with self-set goals, but not for students with teacher-assigned goals. By the end of the experiment, no relationship between anxiety and normalized learning gains could be established for either group. Additionally, it was found that anxiety was not related to goal attainment. These results demonstrate a shift in the control anxiety had over achievement through the use of goals. While there was no significant change in performance-goal orientation for either group over the course of the experiment, both groups experienced a significant drop in mastery-goal orientation by the end of the experiment, suggesting students were more interested in letter grades than truly mastering content. The findings of this study suggest that performance goals are more efficient with seventh grade science students if they are assigned. Furthermore, the use of performance goals within the classroom shows promise as a tool to develop students self-efficacy and self-regulation.

This study investigated the effect of traditional and electronic note taking on student achievement and engagement in a Louisiana high school biology classroom. Over a 20-week period, traditional students (n= 58) took notes using pencil and paper and electronic note takers (n=46) used their laptop computers. Each group of students was given identical pre and posttests covering three units and a practice End of Course exam. Normalized learning gains were compared for each unit and suggest there is no significant difference in academic achievement between the traditional note takers and the electronic note takers. An attitudinal survey was also administered and indicated that both electronic and traditional note takers preferred taking notes traditionally. Observations conducted by the teacher indicated a low occurrence of off task behavior; there were no significant differences between note taking groups. Results that were self-reported by the students show greater off task occurrences, especially within the electronic group. Teachers should carefully consider integrating technology into the note taking process. Since electronic note taking affects student engagement, but does not impact student achievement, allowing students the freedom to choose whichever method they prefer may positively impact classroom culture.

The firefly luciferase complementation assay is widely used as a bioluminescent reporter technology to detect protein-protein interactions in vitro and in vivo. Firefly luciferase oxidates its substrate, luciferin, resulting in the emission of light. A previous study suggests that the firefly luciferase complementation assay has different luminescence kinetics from full length luciferase. The mechanism behind this is still unknown. Although half of the previously published studies utilizing the firefly luciferase complementation assay consider it quantitative. To understand how the molecular reactions and the changes in the affinity of the protein pair affect experimental results, a mathematical model was constructed. This suggests that previously published studies should be considered qualitative, unless an additional experiment is performed. This new model demonstrates that the luminescence measured is not linearly correlated with the affinity of the protein pair. The model is then used to design a new experiment which allows the firefly luciferase complementation assay to be used quantitatively to detect changes of affinity.

The diversity of fishes in the Neotropics consists of nearly 6,000 species, approximately 10% of all vertebrate species on the planet. Evolutionary patterns and processes in fishes are often quite distinct from terrestrial biota, and the study of freshwater fishes can offer insight into understanding evolution and biogeography of regions. One of the major lineages of neotropical freshwater fishes, family Cichlidae, consist of over 500 species in the Neotropics but over 1,600 species overall. The aim of this study is to (1) assess diversification patterns within the family, with a focus on neotropical clades, (2) reassess phylogenetic relationships among northern Middle American cichlids and formally revise the taxonomy of this enigmatic group of fishes, and (3) assess phylogeographic structure within widespread Middle American fishes and begin exploring intrinsic capabilities that may influence our understanding of their biogeographic history. Results show that neotropical cichlids are relatively old in age and their diversity can be attributed to the age of the clade as opposed to an increase or decrease in rate of evolutionary diversification. For the northern Middle American herichthyin cichlids, a revised taxonomy of the group is offered based on robust taxonomic sampling and assessment of morphological characters to define genera. At a more exclusive taxonomic scale, phylogeographic structure is not observed for some lowland neotropical fishes in Middle America. Incorporation of physiological and behavioral data casts doubt on marine dispersal as the sole or primary mechanism of dispersal for these fishes. Overall results show the importance of an integrative approach to undertand the evolution and biogeography of freshwater fishes in the Neotropics.