The Buoyant Behavior of Viral and Bacterial DNA in Alkaline CsCl

In equilibrium density gradient centrifugation, the banding polymer species is electrically neutral. The banding species for a negative polyelectrolyte with a polyanion P_(n)^(-z)n (where n is the degree of polymerization, and z the titration charge per monomer unit) in a CsCl salt gradient is CS_(zn)P_n. If the ion P_(n)^(-z)n is itself a weak acid, it may be titrated to the state P_(n)^(-(Zn+y)) by CsOH; the banding species is then Cs_(zn+y)P_n. Because of the large mass and high effective "density" of a Cs^+ ion, it is to be expected that the buoyant density in a CsCl gradient of a polymer acid will be increased by such a partial alkaline titration with CsOH. This expectation has been confirmed for polyglutamic acid (where z = 0 at low pH). The guanine and thymine monomer units of DNA are weak acids. The present communication is concerned with the increase in buoyant density of DNA in alkaline CsCl solutions. It is well known that the guanine and thymine protons are more readily titrated in denatured DNA than in native DNA. We find that the buoyant density of denatured DNA and of single strand ϕX-174 DNA gradually increases as the pH of the solution is increased beyond pH 9.8. The density of native DNA is not affected until a critical pH > 11 is reached, where the DNA abruptly denatures and increases in density. Similar increases in buoyant density have been observed independently by Baldwin and Shooter in their studies of 5BU[overbar]-substituted DNA's in alkaline solutions

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An Investigation of Affirmative Action Policies and Practices of Recruiting, Hiring, Mentoring and Retention of African American Teachers and Administrators

The purpose of this study was to investigate the affirmative action policies and practices of recruiting, hiring, mentoring and retention of African American teachers and administrators throughout the State of Illinois. Since public elementary and secondary school systems provide numerous and varied jobs in virtually every community in the nation, it is assumed that if a quality education is to be attained, students must be exposed to the variety of cultural perspectives that represent the nation at large (American Association of Colleges of Teacher Education, 1990). This study examined policies and practices of districts throughout the State of Illinois inquiring whether their respective districts actually have active affirmative action policies and a line item set aside for recruitment. The amount of money spent on recruitment and the number of minorities hired annually was directly correlated to the effectiveness of their affirmative action policy. The study also solicited input concerning who should be responsible for recruiting, hiring, mentoring, and retaining African American teachers and administrators. The findings of this study support the assumption that minority teachers and administrative candidates are not choosing teaching and educational administration as a profession because of factors such as: minimal advancement opportunities from the classroom to administrative positions, lack of a strong network to serve as a support structure within the field of education, and difficulty with the National Teachers Examination (NTE). These factors continue to limit the induction of minority teachers into the profession so they can gain the necessary experience to advance to administrative positions

An Investigation of Affirmative Action Policies and Practices of Recruiting, Hiring, Mentoring and Retention of African American Teachers and Administrators

The purpose of this study was to investigate the affirmative action policies and practices of recruiting, hiring, mentoring and retention of African American teachers and administrators throughout the State of Illinois. Since public elementary and secondary school systems provide numerous and varied jobs in virtually every community in the nation, it is assumed that if a quality education is to be attained, students must be exposed to the variety of cultural perspectives that represent the nation at large (American Association of Colleges of Teacher Education, 1990). This study examined policies and practices of districts throughout the State of Illinois inquiring whether their respective districts actually have active affirmative action policies and a line item set aside for recruitment. The amount of money spent on recruitment and the number of minorities hired annually was directly correlated to the effectiveness of their affirmative action policy. The study also solicited input concerning who should be responsible for recruiting, hiring, mentoring, and retaining African American teachers and administrators. The findings of this study support the assumption that minority teachers and administrative candidates are not choosing teaching and educational administration as a profession because of factors such as: minimal advancement opportunities from the classroom to administrative positions, lack of a strong network to serve as a support structure within the field of education, and difficulty with the National Teachers Examination (NTE). These factors continue to limit the induction of minority teachers into the profession so they can gain the necessary experience to advance to administrative positions