Laser Beam Profiling and Crystallographic Analysis

Lasers and x-rays are widely used in the modern world for studying biomolecules. For the purposes of the physics department, future research requires certainty that lasers have Gaussian profiles, though the lasers used often deviate from this ideal. In this project, we investigate methods to measure and analyze laser beam profiles. We first reviewed the theory of Gaussian beams and their properties. We then measured our laser’s profile using two techniques: a knife-edge method and a cell phone photography method. The first involved moving a razor edge across the beam to measure transmitted light, while the second involved visualizing the profile through photographs. The second part of the project involved x-ray crystallography, a powerful technique for determining the three-dimensional structure of molecules. Crystallography analysis involves growing crystals of the molecule of interest and exposing them to x-rays. By analyzing the diffraction pattern, it is possible to reconstruct the molecule’s electron density and determine its precise atomic coordinates. However, crystallography analysis can be challenging due to the data processing and modeling required to interpret the diffraction data. We compared open-source crystallography software and practiced data analysis using publicly available sample diffraction patterns. In summary, we investigated methods to measure and analyze laser beam profiles, including hands-on techniques and imaging. We also discussed x-ray crystallography, a key technique in studying molecular structures. Our work provides the foundation for future optics and crystallography projects

Concept Design for Optical Tweezers to be used in DNA Research

Optical tweezers are a Nobel Prize-winning technology capable of trapping microscopic and sub-microscopic particles using a laser beam. There are several new and useful applications available with the use of optical tweezers. A single optical tweezers set up can cost upwards of two hundred thousand dollars; however, we have designed a cost effective set up to study damaged DNA for under thirty thousand dollars. Using this design, we applied for a grant that would give us the necessary funds to build this set up. The building process itself will be very useful hands-on time learning about the laser set up. In addition, our optical tweezers would be integrated into undergraduate classes

Mechanism of Efficient and Accurate Nucleotide Incorporation Opposite 7,8-Dihydro-8-Oxoguanine by Saccharomyces cerevisiae DNA Polymerase η

Most DNA polymerases incorporate nucleotides opposite template 7,8-dihydro-8-oxoguanine (8-oxoG) lesions with reduced efficiency and accuracy. DNA polymerase (Pol) η, which catalyzes the error-free replication of template thymine-thymine (TT) dimers, has the unique ability to accurately and efficiently incorporate nucleotides opposite 8-oxoG templates. Here we have used pre-steady-state kinetics to examine the mechanisms of correct and incorrect nucleotide incorporation opposite G and 8-oxoG by Saccharomyces cerevisiae Pol η. We found that Pol η binds the incoming correct dCTP opposite both G and 8-oxoG with similar affinities, and it incorporates the correct nucleotide bound opposite both G and 8-oxoG with similar rates. While Pol η incorporates an incorrect A opposite 8-oxoG with lower efficiency than it incorporates a correct C, it does incorporate A more efficiently opposite 8-oxoG than opposite G. This is mainly due to greater binding affinity for the incorrect incoming dATP opposite 8-oxoG. Overall, these results show that Pol η replicates through 8-oxoG without any barriers introduced by the presence of the lesion

Leadership, Organizational Climate, and Perceived Burden of Evidence-Based Practice in Mental Health Services

The use of evidence-based practices (EBPs) is associated with favorable client outcomes, yet perceived burden of using EBPs may affect the adoption and implementation of such practices. Multilevel path analysis was used to examine the associations of transformational leadership with organizational climate, and their associations with perceived burden of using EBPs. Results indicated significant relationships between transformational leadership and empowering and demoralizing climates, and between demoralizing climate and perceived burden of EBPs. We found significant indirect associations of leadership and perceived burden through organizational climate. Findings suggest that further research is needed to examine the extent to which improving leadership and organizational climate may reduce perceived burden and use of EBPs with the ultimate goal of enhancing quality of care