Answer:
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Explanation:
Human topoisomerase I plays an important role in removing positive DNA supercoils that accumulate ahead of replication forks. It also is the target for camptothecin-based anticancer drugs that act by increasing levels of topoisomerase I-mediated DNA scission. Evidence suggests that cleavage events most likely to generate permanent genomic damage are those that occur ahead of DNA tracking systems. Therefore, it is important to characterize the ability of topoisomerase I to cleave positively supercoiled DNA. Results confirm that the human enzyme maintains higher levels of cleavage with positively as opposed to negatively supercoiled substrates in the absence or presence of anticancer drugs. Enhanced drug efficacy on positively supercoiled DNA is due primarily to an increase in baseline levels of cleavage. Sites of topoisomerase I-mediated DNA cleavage do not appear to be affected by supercoil geometry. However, rates of ligation are slower with positively supercoiled substrates. Finally, intercalators enhance topoisomerase I-mediated cleavage of negatively supercoiled substrates but not positively supercoiled or linear DNA. We suggest that these compounds act by altering the perceived topological state of the double helix, making underwound DNA appear to be overwound to the enzyme, and propose that these compounds be referred to as ‘topological poisons of topoisomerase I’
In the following orbital the lone pair on each N atom is present:
N1: sp3,
N2: p,
N3: p,
N4: sp2,
N5: sp2
Sitagliptin is an anti-diabetic drug used to treat type 2 diabetes and is marketed under the brand names Januvia and others. One carbon atom has no pi bonds, while the first nitrogen atom is linked to two hydrogen atoms. It thus possesses sp3 hybridization.
The second nitrogen atom possesses a single pair of electrons and is bound to three other atoms. It is hence sp2 hybridized. The nitrogen atoms in positions 3, 4, and 5 have sp2 hybridization.
The lone pair of nitrogen in the first nitrogen atom is in the sp3 orbital. The second and third nitrogen atoms' only pair of electrons are in p-orbitals. The fourth and fifth nitrogen atoms' lone pair of electrons are in sp2 orbitals.
Here is another question with an answer similar to this about Sitagliptin: brainly.com/question/28275161
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They can encode proteins that provide additional benefits for the bacteria to survive in the local environment. They hold nutrients necessary for the bacteria to survive.
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