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Printable Handouts
Navigable Slide Index
- Introduction
- Altering the sizes of DNA bases
- Two design strategies
- Benzo-expansion strategy
- xDNA: long-term goals
- xDNA = "expanded DNA"
- Structure of adenine and xA
- Structure of thymine and xT
- Size expanded base pairs: too wide for DNA?
- Lack of backbone distortion
- Synthesis of dxA nucleoside phosphoramidite
- Synthesis of dxT nucleoside phosphoramidite
- xDNA bases are fluorescent
- A single expanded pair destabilizes DNA
- When all pairs are expanded, xDNA is very stable
- xDNA can form highly stable helices
- A four-base expanded-size genetic system
- High stability of xDNA compared to DNA
- xDNA hybridization is sequence and size selective
- Solution structure of an xDNA helix
- Major groove
- Minor groove
- Enhanced stacking overlap due to larger base pair
- Strong stacking of size-expanded bases
- yDNA = "wide DNA"
- A new strategy for widening bases: "yDNA"
- The four building blocks of yDNA
- yDNA bases are fluorescent
- Six sequences of yDNA
- Conclusions of xDNA studies to date
- Future plans for xDNA / yDNA
- Two design strategies
- The concept of nonpolar shape mimics
- Thymine and difluorotoluene
- The ability to process non-H-bonding bases
- Single nucleotide insertions
- Efficiency and fidelity for dNTP insertion
- New hypothesis
- Varying steric demand
- Modeling pairs of increasing size
- Increasing steric demand series
- Predictions for DNA polymerase
- Varying steric demand in an enzyme active site (1)
- Varying steric demand in an enzyme active site (2)
- Trends in efficiency: sub-Angstrom increments
- Trends in fidelity across the series
- The goldilocks principle (1)
- The goldilocks principle (2)
- Observations
- Biological relevance?
- The importance of steric effects in vivo
- Conclusions to date
- Why do polymerases prefer larger DNA?
- Questions remaining
- Future plans
- Acknowledgements
Topics Covered
- Chemical and biophysical properties of size-expanded DNA bases (xDNA)
- Structure of xDNA
- Design of benzo-widened DNA bases (yDNA)
- Non-polar nucleoside isosteres
- Base pair replication without hydrogen bonds
- Base analogues with systematically varied size
- Steric effects in DNA replication in vitro and in vivo
Talk Citation
Kool, E. (2020, December 22). The importance of nucleotide size in the chemistry and biology of DNA [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved November 21, 2024, from https://doi.org/10.69645/NZMQ9317.Export Citation (RIS)
Publication History
Financial Disclosures
- Prof. Eric Kool has not informed HSTalks of any commercial/financial relationship that it is appropriate to disclose.
Update Available
The speaker addresses developments since the publication of the original talk. We recommend listening to the associated update as well as the lecture.
- Full lecture Duration: 40:36 min
- Update Interview Duration: 13:59 min
The importance of nucleotide size in the chemistry and biology of DNA
A selection of talks on Biochemistry
Transcript
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0:00
The title of this talk is the importance of
nucleotide size in the chemistry and biology of DNA.
I'm Eric Kool, I'm in the chemistry department at Stanford University.
0:12
In this talk, I'll discuss experiments we've carried out
in which we change the size of DNA bases.
Now, why do we do this?
Three main reasons.
First, is to find out how flexible and adaptable the DNA backbone is.
Second, is to find out how proteins that recognize
DNA depend on the sizes and shapes of DNA bases.
Third, is the design strategy that we'd like to understand how flexible
the DNA is in order to design possible new genetic systems.
0:44
During the talk, I'll discuss two design strategies used in our laboratory,
the use of benzo-expanded DNA bases;
these have Watson-Crick hydrogen bonding groups.
The second strategy is the use of incrementally expanded DNA bases;
these are non-polar molecules that lack hydrogen bonding groups.
We take two different strategies to approach this problem
of the effects of DNA size from two directions.
1:11
In the first part of the talk, I'll discuss
our benzo-expansion strategy for designed DNA bases.
This will involve two sets of molecules,
the first called xDNA and the more recent set called yDNA.
1:26
In our xDNA or expanded DNA project,
we have several long-term goals.
First, is to replace all of the DNA base pairs with ones of our own design.
Second, is to see if these molecules can possess DNA-like functions,
the natural biological functions,
for example, DNA replication.
Third, we hope that there are some applications that may be useful for these molecules,
including detection of nucleic acids and possible imaging of nucleic acids inside cells.
The reasons we think this work is important are two-fold.
First, we're asking if other genetic systems,
other molecular designs could exist in function.
In part, this is a human question that is,
can a person design such a molecule?
Second, it's a biological question;
how did our DNA evolve and could other structures have evolved?
The second important reason we think for doing this is that we believe
that there are possible applications to design genetic systems.
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