The fabrication and characterization of adjustable nanogaps between gold electrodes on chip for electrical measurement of single molecules

This work reports on a new method to fabricate mechanically controllable break junctions (MCBJ) with finely adjustable nanogaps between two gold electrodes on solid state chips for characterizing electron transport properties of single molecules. The simple, low cost, robust and reproducible fabrication method combines conventional photolithography, chemical etching and electrodeposition to produce suspended electrodes separated with nanogaps. The MCBJ devices fabricated by the method can undergo many cycles in which the nanogap width can be precisely and repeatedly varied from zero to several nanometers. The method improves the success rate of the MCBJ experiments. Using these devices the electron transport properties of a typical molecular system, commercially available benzene-1,4-dithiol (BDT), have been studied. The I-V and G-V characteristic curves of BDT and the conductance value for a single BDT molecule established the excellent device suitability for molecular electronics research.NSF [20620130427]; MOST in China [2007DFC40440, 2009CB930703]; State Key Laboratory of Supramolecular Structure and Materials [SKLSSM200701]; Jilin Univ., China ; CNRS (UMR 8640 'PASTEUR'), Ecole Normale Superieure (ENS), University Pierre and Marie Curie (UPMC) ; French Ministry of Research in France through ANR REEL ; US-NSF [DMR-03-05242

Investigating Heat Shock Induced Double Strand Breaks in Caenorhabditis elegans Spermatocyte

42 pages. A thesis presented to the Department of Biology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2017Meiosis is a specialized form of cell division that occurs in sexually reproducing organisms to generate haploid gametes, such as sperm and eggs. Double strand DNA breaks (DSBs) are a form of DNA damage and are intentionally induced in cells during meiosis. It is necessary that these breaks are properly repaired because improper repair can cause infertility, birth defects, miscarriages, or cancer. Unlike other tissues in the body, sperm are known to be sensitive to small fluctuations in temperature; the inability of sperm to thermoregulate in response to high temperature is known to cause male infertility. Previous research in Caenorhabditis elegans has shown that heat shock of adult males results in a dramatic increase in DSBs in the developing sperm of the germline. This phenotype is specific to spermatocytes and independent of spo-11, the enzyme that induces DSBs. This paper examines the effect of a spectrum of heat shock temperatures on the induction of DSBs in C. elegans spermatocytes. Adult male worms were heat shocked and the gonads were dissected and stained with antibody to mark DSBs. The results show a relatively uniform quantity of breaks from 25-33°C with a threshold increase in the number of breaks happening at 34°C. Additional DSBs were induced at heat shock temperatures above 34°C. These results indicate that spermatocytes are extremely sensitive to a slight fluctuation in temperature and that deviation from a narrow isotherm leads to the induction of an abundance of DNA damage. This work has helped to increase our understanding of how small temperature fluctuations contribute to the induction of DNA damage in spermatocytes, which can ultimately lead to male infertility