Feb
28
DNA Damage and Protection
Genetic Engineering
Frontiers of Biomedical Engineering (BENG 100)
AZT’s Mechanism of Antiviral Activity
This animation shows the chemical details of how the antiviral drug AZT acts as a chain terminator in replicating DNA. The term “chain terminator” is a difficult concept to explain to those students who do not have a good grasp of nucleic acid chemistry. It is important to understand the exact mechanisms of DNA replication at the atomic resolution level as a prerequisite for understanding AZT action. This animation helps the students to visualize the whole chemical process of chain termination.
This animation consists of four small segments and shows how a normal strand of DNA unravels in preparation for replication.
In the next part of the animation, two base pairs are added to a growing DNA strand. Worth noting here is the fact that each new base pair is attacked by the 3′-OH on the existing DNA strand. This OH group attacks the incoming base pair’s a-phosphate group, leading to the formation of a bond between the incoming base pair and the growing DNA strand while causing the release of a diphosphate group.
In the third segment of the animation, AZT is converted by kinases to AZT-monophosphate (AZT-P), AZT-diphosphate (AZT-PP), and AZT-triphosphate (AZT-PPP), respectively. This step must occur in vivo so that AZT can be successfully incorporated into the replicating strand of DNA.
In the final portion of the animation, AZT-PPP is added to the strand. However, AZT lacks the 3′-OH. Instead, it contains N3 at this critical position. Consequently, once it is added, replication comes to a halt. This fact is illustrated in the final segment of the animation where the two base pairs approach the growing strand but are turned away. Therefore, once added to the growing DNA strand, AZT causes DNA chain termination. In doing so, it disrupts the virus’ mechanism for replication and survival.
3D DNA model
This newly created 3D DNA model is of the highest quality on the market today and should be of interest to anyone in the biomedical field.
While dealing with the great deal of complexity in DNA structure, this model still maintains visual clarity while detailing the structure of the double helix.
Similar to previous models, this 3D model depicts the right-handed double helical nature of a DNA strand with its major and minor grooves, but goes further in detail by explicitly defining each base and its skeletal structure. Each adenine and guanine base is modeled to show how it bonds to its complementary thymine and cytosine, respectively. The skeletal structure of the phosphodiester backbones in this helix are also included with their bonds to the heterocyclic bases previously mentioned. Every base and phosphate group is individually grouped for easy isolation and identification.
For Your Health - DNA Cancer Research
Two aspects of cancer are featured on this episode of For Your Health, a way that lasers may be used in a new cutting edge treatment and how DNA research is changing the way doctors think about tumor growth. Hosts Charna Davis Wiese and Ed Heiland also explore new developments in treatment of speech problems. (2008)