Balancing interactions in proline-based receptors for chiral recognition of l-/d-DOPA

In the article the results of the quantum chemical study of copper (II) solvato-complexes with acetonitrile (AN), tetrafluoroborate anion (BF4–) and 3-hydroxyflavone (flv) of the composition [Cu(AN)6]2+, [Cu(BF4)(AN)5]+, [Cu(flv)(AN)5]2+, [Cu(flv)(BF4)(AN)4]+ are presented. Calculations were done using density function theory (DFT) on the M06-2X/6-311++G(d,p) level of theory. Obtained results were interpreted in terms of complexes geometry and topology of electron density distribution using non-covalent interactions (NCI) approach. It was shown that flv molecule is a monodentate ligand in copper (II) complexes and coordinates central atom via carbonyl oxygen. Intramolecular hydrogen bond that exists in an isolated flv molecule was found to be broken upon [Cu(flv)(AN)5]2+ complex formation. In [Cu(flv)(AN)5]2+ complex, a significant rotation of phenyl ring over the planar chromone fragment was spotted as a consequence of intramolecular hydrogen bond breaking. Upon inclusion of BF4– anion to the first solvation shell of Cu2+, an intracomplex hydrogen bond was formed between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion. NCI analysis had shown that a hydrogen bond between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion is significantly stronger than intramolecular hydrogen bond in an isolated flv molecule. In addition, flexible phenyl ring of flv molecule in [Cu(flv)(BF4)(AN)4]+ complex was found to be internally stabilized by the weak van der Waals attraction between oxygen atoms of chromone ring and phenyl hydrogens. These evidences led to a conclusion that [Cu(flv)(BF4)(AN)4]+ complex is more stable, comparing to the in [Cu(flv)(AN)5]2+ complex.

Download Full-text

New Substituted Benzoylthiourea Derivatives: From Design to Antimicrobial Applications

Molecules ◽

10.3390/molecules25071478 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1478

Author(s):

Carmen Limban ◽

Mariana Carmen Chifiriuc ◽

Miron Teodor Caproiu ◽

Florea Dumitrascu ◽

Marilena Ferbinteanu ◽

...

Keyword(s):

Phenyl Ring ◽

Fluorine Atom ◽

Antibacterial Effect ◽

Dna Gyrase ◽

Therapeutic Agents ◽

Antibiofilm Activity ◽

X Ray Diffraction ◽

X Ray ◽

E Coli ◽

New Compounds

The increasing threat of antimicrobial resistance to all currently available therapeutic agents has urged the development of novel antimicrobials. In this context, a series of new benzoylthiourea derivatives substituted with one or more fluorine atoms and with the trifluoromethyl group have been tested, synthesized, and characterized by IR, NMR, CHNS and crystal X-ray diffraction. The molecular docking has provided information regarding the binding affinity and the orientation of the new compounds to Escherichia coli DNA gyrase B. The docking score predicted the antimicrobial activity of the studied compounds, especially against E. coli, which was further demonstrated experimentally against planktonic and biofilm embedded bacterial and fungal cells. The compounds bearing one fluorine atom on the phenyl ring have shown the best antibacterial effect, while those with three fluorine atoms exhibited the most intensive antifungal activity. All tested compounds exhibited antibiofilm activity, correlated with the trifluoromethyl substituent, most favorable in para position.

Download Full-text

Diazonium Gold Salts as Novel Surface Modifiers: What Have We Learned So Far?

Surfaces ◽

10.3390/surfaces3020014 ◽

2020 ◽

Vol 3 (2) ◽

pp. 182-196 ◽

Cited By ~ 1

Author(s):

Ahmad A. L. Ahmad ◽

Bizuneh Workie ◽

Ahmed A. Mohamed

Keyword(s):

Phenyl Ring ◽

Review Paper ◽

Molecular Nitrogen ◽

Fine Tuning ◽

Metal Salts ◽

Diazonium Salts ◽

Recent Contribution ◽

Surface Modifiers ◽

Gold Salts ◽

Potential Applications

The challenges of diazonium salts stabilization have been overcome by their isolation as metal salts such as tetrachloroaurate(III). The cleavage of molecular nitrogen from diazonium salts even at very low potential or on reducing surfaces by fine tuning the substituents on the phenyl ring expanded their applications as surface modifiers in forensic science, nanomedicine engineering, catalysis and energy. The robustness of the metal–carbon bonding produced from diazonium salts reduction has already opened an era for further applications. The integration of experimental and calculations in this field catalyzed its speedy progress. This review provides a narrative of the progress in this chemistry with stress on our recent contribution, identifies potential applications, and highlights the needs in this emerging field. For these reasons, we hope that this review paper serves as motivation for others to enter this developing field of surface modification originating from diazonium salts.

Download Full-text

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.16.22 ◽

2020 ◽

Vol 16 ◽

pp. 190-199

Author(s):

Vuyisa Mzozoyana ◽

Fanie R van Heerden ◽

Craig Grimmer

Keyword(s):

Single Crystal ◽

Phenyl Ring ◽

Fluorine Atom ◽

Nmr Spectra ◽

Intramolecular Interaction ◽

X Ray ◽

Solution State ◽

H Nmr ◽

Mild Conditions ◽

C Nmr

4-(2-Fluorophenyl)-7-methoxycoumarin (6) was synthesized by Pechmann reaction under mild conditions via a three-step reaction. The solution-state 1H NMR spectra of 6 showed a strong intramolecular interaction between F and H5 (J FH = 2.6 Hz) and 13C NMR suggested that this C–F···H–C coupling is a through-space interaction. The 2D 19F-{1H} HOESY and 1H-{19F} 1D experiments were done to confirm this F···H interaction. The single crystal X-ray structure and the DFT-optimized structure showed that the fluorinated phenyl ring favors the orientation with the fluorine atom closer to H5 than H3. The X-ray structure also showed the existence of the intermolecular C–F···H–C interaction.

Download Full-text

Effect of Solution Composition Variables on Electrospun Alginate Nanofibers: Response Surface Analysis

Polymers ◽

10.3390/polym11040692 ◽

2019 ◽

Vol 11 (4) ◽

pp. 692 ◽

Cited By ~ 7

Author(s):

Janja Mirtič ◽

Helena Balažic ◽

Špela Zupančič ◽

Julijana Kristl

Keyword(s):

Molecular Weight ◽

Response Surface ◽

Polymer Blend ◽

Polymer Concentration ◽

Electrospun Nanofibers ◽

Complex Viscosity ◽

Fine Tuning ◽

Major Influence ◽

Solution Composition ◽

Poly Ethylene

Alginate is a promising biocompatible and biodegradable polymer for production of nanofibers for drug delivery and tissue engineering. However, alginate is difficult to electrospin due to its polyelectrolyte nature. The aim was to improve the ‘electrospinability’ of alginate with addition of exceptionally high molecular weight poly(ethylene oxide) (PEO) as a co-polymer. The compositions of the polymer-blend solutions for electrospinning were varied for PEO molecular weight, total (alginate plus PEO) polymer concentration, and PEO proportion in the dry alginate–PEO polymer mix used. These were tested for rheology (viscosity, complex viscosity, storage and loss moduli) and conductivity, and the electrospun nanofibers were characterized by scanning electron microscopy. One-parameter-at-a-time approach and response surface methodology (RSM) were used to optimize the polymer-blend solution composition to obtain defined nanofibers. Both approaches revealed that the major influence on nanofiber formation and diameter were total polymer concentration and PEO proportion. These polymer-blend solutions of appropriate conductivity and viscosity enabled fine-tuning of nanofiber diameter. PEO molecular weight of 2–4 million Da greatly improved the electrospinnability of alginate, producing nanofibers with >85% alginate. This study shows that RSM can be used to design nanofibers with optimal alginate and co-polymer contents to provide efficient scaffold material for regenerative medicine.

Download Full-text

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C-F…H-C bond

10.3762/bxiv.2019.124.v1 ◽

2019 ◽

Author(s):

Vuyisa Mzozoyana ◽

Fanie R van Heerden ◽

Craig Grimmer

Keyword(s):

Single Crystal ◽

Phenyl Ring ◽

Fluorine Atom ◽

Nmr Spectra ◽

Intramolecular Interaction ◽

X Ray ◽

Solution State ◽

H Nmr ◽

Mild Conditions ◽

C Nmr

4-(2-fluorophenyl)-7-methoxycoumarin (6) was synthesized by Pechmann reaction under mild conditions via a three step-reaction. The solution-state 1H NMR spectra of 6 showed a strong intramolecular interaction between F and H5 (J FH = 2.6 Hz) and 13C NMR suggested that this C-F…H-C coupling is a through-space interaction. The 2‑D HOESY spectrum and 1H‑{19F} 1‑D spectrum were also done to confirm this F…H interaction. The single crystal X-ray structure and the DFT-optimized structure showed that the fluorinated phenyl ring favours the orientation with the fluorine atom is closer to H5 than H3. The X-ray structure also showed the existence of the intermolecular C-F…H-C interactions.

Download Full-text

Fine-Tuning Futures

ASHA Leader ◽

10.1044/leader.fq.22062017.np ◽

2017 ◽

Vol 22 (6) ◽

Author(s):

Christi Miller

Keyword(s):

Fine Tuning

Download Full-text

Food Safety Security: A new Concept for Enhancing Food Safety Measures

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000114 ◽

2012 ◽

Vol 82 (3) ◽

pp. 216-222 ◽

Cited By ~ 4

Author(s):

Venkatesh Iyengar ◽

Ibrahim Elmadfa

Keyword(s):

Food Safety ◽

Hazard Analysis ◽

Warning System ◽

Shared Responsibility ◽

Fine Tuning ◽

Strategic Action ◽

Surveillance Network ◽

Measurement Systems ◽

Critical Control Points ◽

The Impact

The food safety security (FSS) concept is perceived as an early warning system for minimizing food safety (FS) breaches, and it functions in conjunction with existing FS measures. Essentially, the function of FS and FSS measures can be visualized in two parts: (i) the FS preventive measures as actions taken at the stem level, and (ii) the FSS interventions as actions taken at the root level, to enhance the impact of the implemented safety steps. In practice, along with FS, FSS also draws its support from (i) legislative directives and regulatory measures for enforcing verifiable, timely, and effective compliance; (ii) measurement systems in place for sustained quality assurance; and (iii) shared responsibility to ensure cohesion among all the stakeholders namely, policy makers, regulators, food producers, processors and distributors, and consumers. However, the functional framework of FSS differs from that of FS by way of: (i) retooling the vulnerable segments of the preventive features of existing FS measures; (ii) fine-tuning response systems to efficiently preempt the FS breaches; (iii) building a long-term nutrient and toxicant surveillance network based on validated measurement systems functioning in real time; (iv) focusing on crisp, clear, and correct communication that resonates among all the stakeholders; and (v) developing inter-disciplinary human resources to meet ever-increasing FS challenges. Important determinants of FSS include: (i) strengthening international dialogue for refining regulatory reforms and addressing emerging risks; (ii) developing innovative and strategic action points for intervention {in addition to Hazard Analysis and Critical Control Points (HACCP) procedures]; and (iii) introducing additional science-based tools such as metrology-based measurement systems.

Download Full-text