Transcript 0_Glycine_GO_NMR

Structure sequence during Optimization
GLYCINE Molecule Geometrical Optimization by
Proton
Transfer
GAMESS Computational SOFTWARE at http://www.webmo.net
Hartree-Fock SCF Method, STO3G basis set
90◦
?
STRUCTURE SEQUENCE as Obtained at iterative steps till
Convergence are EXAMINED for the possible inferences from
the Intermediate steps
In this
particular
instance
Optimization procedures started
with
Nonionic
formconvergence
of this
required 45 iterative
steps.
And, the iterative
alpha amino acid, results in converging
with the
nonionic
stage is indicated by the step numbers
structure. When the Zwitterionic Form is the input
structure, convergence occurs with the nonionic form as
the final stabilized form.
The Consequences are illustrated with the
Calculation of NMR spectra for the
intermediate structures and monitor for the
spectral changes corresponding to the step
wise structural changes.
A detailed image of this result for display
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S Aravamudhan WMBS NEHU
25-29 Oct 2010
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0
5
7
10
32
22
14
input
Illustrative
Movie of this
structure
sequence
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output
S Aravamudhan WMBS NEHU
25-29 Oct 2010
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A detail
ZWITTER
ION
Non ionic form
GLYCINE
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S Aravamudhan WMBS NEHU
25-29 Oct 2010
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Particularly take note of the Proton No 8 and its NMR peak
location; does proton 8 turn out to be typical amide proton
and why not any of the other two attached to the nitrogen?
An Illustration of the
possibility of
calculating NMR
chemical shifts for
Glycine and the full
assignment of the
peak position to the
proton location in the
molecule. Thus the
upfield-down field
changes can be
associated with the
variation in the
geometry and the
molecular electronic
structure
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S Aravamudhan WMBS NEHU
25-29 Oct 2010
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Proton 8
An example of
Experimental
13C NMR
Spectra
The CMR image
enlarged view
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S Aravamudhan WMBS NEHU
25-29 Oct 2010
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Is it possible to identify these NMR spectra as belonging to any
of the spectra obtainable for GLYCINE in several of the
variable conditions in a BIOLOGICAL environment?
This question again has to be first of all addressed to the
chemical conditions like pH and solvent nature to find out
whether it is possible to get a set of spectra in the same
sequence as it occurs in the isolated molecule geometry
optimization. Since such experimental spectra would have to
be acquired under variety of conditions (mostly in low
concentration solution of glycine), it may not be immediate that
a conclusion for generalizing can be found. The spectral data
from the currently available NMR data base are not adequate
and it is necessary to alter the experimental conditions with the
specific target of obtaining a particular spectral pattern as
obtained by the theoretical calculation.
A typical data base documentation of Experimental PMR spectrum of Glycine
A correlation of the theoretical scales and experimental scales for chemical shifts
Computed and Experimental 13C NMR spectra
4/10/2016 9:23 PM
S Aravamudhan WMBS NEHU
25-29 Oct 2010
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