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Naturally Occurring Polymers—Animals
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
The telomerase contains RNA, which is used as the template for making telomeres, and a protein part that resembles reverse transcriptase, the enzyme responsible for the production of transposons and retroviruses. Telomerase acts to repair the ends of chromosomes, relengthening the telomere ends. Thus, the lack of telomerase appears to cause the aging and eventual death of at least some of our cells. The relation to aging is much less certain, and surely more complicated. Thus, those with Werner's syndrome, where rapid aging occurs, start out with the same average length of telomers, but the telomers shorten more rapidly so that at least cell aging involves not only the length of telomers but also the rate at which they become shorter. Recently, it was found that certain genes on chromosome 6 appear with differing versions for long-lived men, and other versions for long-lived women.
DNA Structure, Sequencing, Synthesis, and Modification: Making Biology Molecular
Published in Richard J. Sundberg, The Chemical Century, 2017
DNA can also be cloned from RNA. This approach is particularly useful in obtaining the genes connected to specific proteins by targeting the corresponding m-RNA. In this case a reverse transcriptase is used to obtain the complementary DNA sequence, called cDNA. The process begins with isolation of all of the RNA from a particular cell line. The m-RNA is then separated, taking advantage that it contains a “polyadenylate tail” and therefore can be bound by a poly-T matrix. The purified collection of m-RNA molecules are then converted into the corresponding DNA by a reverse transcriptase. The c-DNA corresponds only to the protein sequence, because the non-coding portions (introns) have been removed during m-RNA formation. The c-DNA, in turn, can be converted to double stranded DNA by a DNA polymerase. Finally, the double stranded DNA is modified to add restriction sites that will permit its incorporation into the bacteriophage vector. Cloning then proceeds as described for DNA.
Prophylaxis and Chemotherapy
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Heather D. Stockdale, Jennifer A. Spencer, Byron L. Blagburn
HAART increases CD4+ T-cell counts and inhibits viral replication using a combination of nucleoside and non-nucleoside reverse transcriptase inhibitors (NNRTIs) and HIV protease inhibitors (Table 9.2) (Cacciò and Pozio, 2006). In treating cryptosporidiosis with HAART, an NNRTI or protease inhibitor (PI) is normally used in conjunction with two or more nucleoside reverse transcriptase inhibitors (NRTIs) (Ives et al., 2001). Nucleoside analogs or NRTIs, target reverse transcriptase via competitive binding and inhibit DNA synthesis (Hoffmann and Mulcahy, 2006b). NNRTI also target reverse transcriptase, binding noncompetitively and blocking nearby active sites. This will slow DNA synthesis (Hoffmann and Mulcahy, 2006a). PIs inhibit HIV protease and proteolytic splicing, preventing the viral particles from becoming infective (Hoffmann and Mulcahy, 2006c). Cryptosporidiosis becomes chronic in immunocompromised patients with CD4+ T-cell counts lower than 180/μL (Carr et al., 1998) and life threatening in patients with CD4+ T-cell counts lower than 50/μL (Hoffmann, 2006). In these patients, improving the immune system to levels comparable to a healthy individual with HAART results in self-limiting diarrhea and resolution of cryptosporidiosis (Hoffmann, 2006). A study involving more than 3000 HIV-infected patients, over a 5-year period, undergoing treatment with antiretroviral combinations of NRTIs and PIs, showed a decreasing incidence of opportunistic infections and death. The incidence of cryptosporidiosis decreased from 0.8/100 patients to 0.1/100 patients (Moore and Chaisson, 1999).
New experimental low-cost nanoscience technology for formulation of silver nanoparticles-activated carbon composite as a promising antiviral, biocide, and efficient catalyst
Published in Journal of Experimental Nanoscience, 2022
H. A. Fetouh, H. M. Abd-Elnaby, M. S. Alsubaie, E. R. Sallam
Hepatitis A virus (HAV) is a DNA virus that causes acute hepatitis leading to chronic hepatitis, liver cirrhosis and hepatic cancer. About four hundred millions HAV carriers are infected and more than one million deaths worldwide are reported annually due to HAV-related complications. Effective vaccination of selective antiviral therapeutic drugs alternatives alpha interferon against HAV infection is required. In HAV life cycle, antiviral chemotherapy targets reverse transcription step of pregenome using endogenous viral reverse transcriptase enzyme to incorporate nucleotide analogues in the minus strand of DNA. Nucleotide analogues competitively inhibit reverse transcriptase enzyme. Heterocyclic compounds such as pyrimidine's and diazoles have selective antiviral activities such as Lamivudine, a retroviral inhibitor for HAV replication both in vitro and in vivo. 1-hydroxy-4-nitro-6-trifluoromethyl benzotriazole is an antiviral compound for 12 DNA and RNA viruses including SARS and middle east respiratory syndrome (MERS–CoV) via inactivation of SARS 3CL protease enzyme [9]. However, the synthesis roots for these organic compounds are very complicated and involve various toxic organic compounds [14,16].
Developing mitochondrial DNA field-compatible tests
Published in Critical Reviews in Environmental Science and Technology, 2022
Bidhan C. Dhar, Christina E. Roche, Jay F. Levine
Polymerase chain reaction is used to amplify DNA specimens, particularly for enrichment of small-scale genomes like mtDNA (Guo et al., 2012). The PCR technique was first developed to amplify a short fragment of DNA in vitro (Saiki et al., 1985). It rapidly generates millions to billions of copies of specific fragments of DNA from a small fragment of starting DNA. These PCR reactions can also be used to detect RNA by initially applying the enzyme reverse transcriptase (RT) to transcribe RNA into DNA before amplification. Conventional PCR targeting mtDNA played a transformative role in medical and veterinary diagnostics informing the identification and medical management of mitochondrial associated genetic disorders (Schon et al., 2012), and cancer (Chatterjee et al., 2006) and has played a key role in forensic investigations (Phillips, 2008; Zapico & UBelaker, 2013), molecular ecology, population genetics (Deiner et al., 2017; Hebert et al., 2003), and environmental monitoring (Motlagh and Yang, 2019; Roslev & Bukh, 2011).
Environmental sampling for disease surveillance: Recent advances and recommendations for best practice
Published in Journal of the Air & Waste Management Association, 2023
Joshua L. Santarpia, Elizabeth Klug, Ashley Ravnholdt, Sean M. Kinahan
Polymerase chain reaction (PCR and various types):a technique that can copy specific DNA segments millions of times using special enzymes (polymerases). Quantitative PCR (qPCR) is a method to quantify the initial amount of DNA using fluorescent molecules. Reverse transcriptase (RT) PCR is a method to first convert RNA to DNA, using an enzyme, and then amplify it using the PCR process.