scholarly journals NMR-Guided Directed Evolution

2021 ◽  
Author(s):  
Ivan Korendovych ◽  
Sagar Bhattacharya ◽  
Eleanora Margheritis ◽  
Katsuya Takahashi ◽  
Alona Kulesha ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Directed Evolution ◽  
A Priori ◽  
Catalytic Efficiency ◽  
Simple Approach ◽  
Chemical Shift Perturbation ◽  
Full Potential ◽  
Proof Of Concept ◽  
Nuclear Magnetic Resonance Spectra

Abstract Directed evolution can rapidly achieve dramatic improvements in the properties of a protein or bestow entirely new functions on it. We have discovered a strong correlation between the probability of finding a productive mutation at a particular position of a protein and a chemical shift perturbation in Nuclear Magnetic Resonance spectra upon addition of an inhibitor for the chemical reaction it promotes. In a proof-of-concept study we converted myoglobin, a non-enzymatic protein, into the most active Kemp eliminase reported to date using only three mutations. The observed levels of catalytic efficiency are on par with the levels shown by natural enzymes. This simple approach, that requires no a priori structural or bioinformatic knowledge, is widely applicable and will unleash the full potential of directed evolution.

Raman, infrared and n.m.r. studies of the graphite hydrofluorides C x F 1-δ (HF) δ (2 ≤ x ≤ 5)

1985 ◽  
Vol 314 (1528) ◽  
pp. 179-187 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Carbon Atom ◽  
Contact Time ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Vibrational Modes ◽  
Nuclear Magnetic Resonance Spectra ◽  
Angle Spinning ◽  
Two Peaks

Raman spectra of C x F 1-δ (HF) δ ( x /δ ≈ 12) show bands at 1600, 1355 and 839 cm -1 , which are attributed to graphite-like vibrational modes of the carbon atom sheets. The infrared spectra show, in addition to graphite-like bands, absorptions at 1270 and 1100 cm -1 , which are attributed to C-F stretching. Variable contact-time cross-polarized magic-angle spinning 13 C nuclear magnetic resonance spectra (c.p.m.a.s. 13 C n.m.r.) have been obtained for x = 2.05 and 3.70. In both spectra, two peaks ( + 135/10 6 and + 88/10 6 chemical shift from TMS) are seen, which are attributed, respectively, to graphitic and C-F carbons. The ratio of graphitic to C-F carbon atoms has been found to be 1.6(2) : 1 in C 2.05 F 0.82 (HF) 0.18 . The carbon atom sheets in C x F 1-δ (HF) δ appear to be very similar to those in pristine graphite. The bonding of fluorine to carbon is highly ionic. Bonding models are discussed.

Carbon-13 nuclear magnetic resonance spectra of N-, O-, and S-methylated uracil and thiouracil derivatives

1978 ◽  
Vol 56 (5) ◽  
pp. 725-729 ◽  
Author(s):  
Ian W. J. Still ◽  
Nick Plavac ◽  
David M. McKinnon ◽  
Mohinder S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
General Type ◽  
Chemical Shifts ◽  
Pyrimidine Derivatives ◽  
Aromatic Substituent ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of ◽  
Thiouracil Derivatives ◽  
C Nmr

13C nmr chemical shifts have been recorded for a number of uracil, thiouracil, and pyrimidine derivatives. These data are discussed in relation to what is known of the lactam–lactim tautomerism in such systems and possible correlations of chemical shifts with normal aromatic substituent chemical shift parameters. The chemical shifts for the CH3 groups in simple methylated derivatives of uracil are very characteristic of the site of methylation and should prove useful as a tool for assigning structures to alkylated derivatives of this general type.

Nuclear magnetic resonance spectra of ortho-, meta-, and para-difluorobenzenes in a nematic liquid crystal solvent

1969 ◽  
Vol 47 (6) ◽  
pp. 1057-1065 ◽  
Author(s):  
C. T. Yim ◽  
D. F. R. Gilson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Liquid Crystal ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Nematic Liquid Crystal ◽  
Hydrogen Atoms ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The proton and fluorine magnetic resonance spectra of ortho-, meta-, and para-difluorobenzene dissolved in a nematic liquid crystal solvent have been analyzed. Expressions for the anisotropy of the fluorine chemical shift were obtained but an attempt to fit these to the Karplus and Das theory failed. Hydrogen atoms ortho to fluorine show small displacements from their expected positions.

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