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Related Concept Videos

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)01:19

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)

Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
Stability of Conjugated Dienes01:28

Stability of Conjugated Dienes

Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...

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Synthesizing Amino Acids Modified with Reactive Carbonyls in Silico to Assess Structural Effects Using Molecular Dynamics Simulations
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4D-QSAR study of HEPT derivatives by electron conformational-genetic algorithm method.

L Akyüz1, E Sarıpınar, E Kaya

  • 1Department of Chemistry, Erciyes University, Kayseri, Turkey.

SAR and QSAR in Environmental Research
|March 29, 2012
PubMed
Summary

This study introduces the EC-GA method to predict anti-HIV-1 activity in HEPT derivatives. The developed quantitative structure-activity relationship (QSAR) model accurately predicts drug efficacy and designs novel compounds.

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Area of Science:

  • Medicinal Chemistry
  • Computational Chemistry
  • Pharmacology

Background:

  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are crucial in HIV-1 treatment.
  • 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio) thymine (HEPT) derivatives are a significant class of NNRTIs.
  • Understanding structure-activity relationships is key to developing more effective anti-HIV-1 drugs.

Purpose of the Study:

  • To develop a quantitative structure-activity relationship (QSAR) model for predicting the anti-HIV-1 activity of HEPT derivatives.
  • To apply the hybrid electron conformational-genetic algorithm optimization (EC-GA) method for pharmacophore explanation and activity prediction.
  • To design novel HEPT derivatives with potentially enhanced anti-HIV-1 activity.

Main Methods:

  • Application of the EC-GA hybrid 4D-QSAR approach.
  • Partitioning of 115 HEPT derivatives into training and test sets.
  • Construction and analysis of four QSAR models, with a focus on Model 4 utilizing random partitioning and 11 descriptors.

Main Results:

  • Model 4 demonstrated robust statistical performance in regression (r²=0.867 training, r²=0.923 test) and cross-validation (q²=0.811).
  • The EC-GA method provided a quantitatively consistent QSAR model for predicting anti-HIV-1 activity.
  • Eight novel HEPT compounds were theoretically designed using the validated Model 4.

Conclusions:

  • The EC-GA method is effective for developing predictive QSAR models for NNRTIs.
  • The study successfully identified key electronic and geometrical descriptors influencing anti-HIV-1 activity.
  • The designed novel compounds represent promising candidates for further experimental investigation in HIV-1 therapy.