| 1. |
- Denisova V, Aleksandra, et al.
(författare)
-
A Computational Investigation of the Substituent Effects on Geometric, Electronic, and Optical Properties of Siloles and 1,4-Disilacyclohexa-2,5-dienes
- 2017
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 22:3
-
Tidskriftsartikel (refereegranskat)abstract
- Thirty two differently substituted siloles 1a–1p and 1,4-disilacyclohexa-2,5-dienes 2a–2p were investigated by quantum chemical calculations using the PBE0 hybrid density functional theory (DFT) method. The substituents included σ-electron donating and withdrawing, as well as π-electron donating and withdrawing groups, and their effects when placed at the Si atom(s) or at the C atoms were examined. Focus was placed on geometries, frontier orbital energies and the energies of the first allowed electronic excitations. We analyzed the variation in energies between the orbitals which correspond to HOMO and LUMO for the two parent species, here represented as ΔεHL, motivated by the fact that the first allowed transitions involve excitation between these orbitals. Even though ΔεHL and the excitation energies are lower for siloles than for 1,4-disilacyclohexa-2,5-dienes the latter display significantly larger variations with substitution. The ΔεHL of the siloles vary within 4.57–5.35 eV (ΔΔεHL = 0.78 eV) while for the 1,4-disilacyclohexa-2,5-dienes the range is 5.49–7.15 eV (ΔΔεHL = 1.66 eV). The excitation energy of the first allowed transitions display a moderate variation for siloles (3.60–4.41 eV) whereas the variation for 1,4-disilacyclohexa-2,5-dienes is nearly doubled (4.69–6.21 eV). Cyclobutadisiloles combine the characteristics of siloles and 1,4-disilacyclohexa-2,5-diene by having even lower excitation energies than siloles yet also extensive variation in excitation energies to substitution of 1,4-disilacyclohexa-2,5-dienes (3.47–4.77 eV, variation of 1.30 eV).
|
|
| 2. |
- Kostag, Marc, et al.
(författare)
-
Recent Advances in Solvents for the Dissolution, Shaping and Derivatization of Cellulose : Quaternary Ammonium Electrolytes and their Solutions in Water and Molecular Solvents.
- 2018
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 23:3
-
Tidskriftsartikel (refereegranskat)abstract
- There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., without covalent bond formation. The use of ionic liquids, ILs, has generated much interest because of their structural versatility that results in efficiency as cellulose solvents. Despite some limitations, imidazole-based ILs have received most of the scientific community's attention. The objective of the present review is to show the advantages of using quaternary ammonium electrolytes, QAEs, including salts of super bases, as solvents for cellulose dissolution, shaping, and derivatization, and as a result, increase the interest in further investigation of these important solvents. QAEs share with ILs structural versatility; many are liquids at room temperature or are soluble in water and molecular solvents (MSs), in particular dimethyl sulfoxide. In this review we first give a historical background on the use of QAEs in cellulose chemistry, and then discuss the common, relatively simple strategies for their synthesis. We discuss the mechanism of cellulose dissolution by QAEs, neat or as solutions in MSs and water, with emphasis on the relevance to cellulose dissolution efficiency of the charge and structure of the cation and. We then discuss the use of cellulose solutions in these solvents for its derivatization under homogeneous and heterogeneous conditions. The products of interest are cellulose esters and ethers; our emphasis is on the role of solvent and possible side reactions. The final part is concerned with the use of cellulose dopes in these solvents for its shaping as fibers, a field with potential commercial application.
|
|
| 3. |
- Ali, Sara E., et al.
(författare)
-
Profiling Metabolites and Biological Activities of Sugarcane (Saccharum officinarum Linn.) Juice and Its Product Molasses via a Multiplex Metabolomics Approach
- 2019
-
Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 24:5
-
Tidskriftsartikel (refereegranskat)abstract
- Sugarcane (Saccharum officinarum L.) is an important perennial grass in the Poaceae family cultivated worldwide due to its economical and medicinal value. In this study, a combined approach using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy was employed for the large-scale metabolite profiling of sugarcane juice and its by-product molasses. The polyphenols were analysed via UPLC-UV-ESI-MS, whereas the primary metabolites such as sugars and organic and amino acids were profiled using NMR spectroscopy and gas chromatography/mass spectrometry (GC/MS). UPLC/MS was more effective than NMR spectroscopy or GC/MS for determining differences among the metabolite compositions of the products. Under the optimized conditions, UPLC/MS led to the identification of 42 metabolites, including nine flavonoids, nine fatty acids, and two sterols. C/O Flavone glycosides were the main subclass detected, with tricin-7-O-deoxyhexosyl glucuronide being detected in sugarcane and molasses for the first time. Based on GC/MS analysis, disaccharides were the predominant species in the sugarcane juice and molasses, with sucrose accounting for 66% and 59%, respectively, by mass of all identified metabolites. The phenolic profiles of sugarcane and molasses were further investigated in relation to their in vitro antioxidant activities using free radical scavenging assays such as 2,2-Diphenyl-1-picrylhydrazyl free radical-scavenging ability (DPPH), Trolox equivalent antioxidant capacity (TEAC) and ferric reducing antioxidant power (FRAP). In view of its higher total phenolic content (TPC) (196 +/- 2.1 mg GAE/100 g extract) compared to that of sugarcane juice (93 +/- 2.9 mg GAE/100 g extract), molasses exhibited a substantially higher antioxidant effect. Interestingly, both extracts were also found to inhibit alpha-glucosidase and alpha-amylase enzymes, suggesting a possible antihyperglycaemic effect. These findings suggest molasses may be a new source of natural antioxidants for functional foods.
|
|
| 4. |
- Allgardsson, Anders, et al.
(författare)
-
An unusual dimeric inhibitor of acetylcholinesterase : cooperative binding of crystal violet
- 2017
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 22:9
-
Tidskriftsartikel (refereegranskat)abstract
- Acetylcholinesterase (AChE) is an essential enzyme that terminates cholinergic transmission by a rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for treatment of various cholinergic deficiencies, including Alzheimer's disease and myasthenia gravis. In a previous high throughput screening campaign, we identified the dye crystal violet (CV) as an inhibitor of AChE. Herein, we show that CV displays a significant cooperativity for binding to AChE, and the molecular basis for this observation has been investigated by X-ray crystallography. Two monomers of CV bind to residues at the entrance of the active site gorge of the enzyme. Notably, the two CV molecules have extensive intermolecular contacts with each other and with AChE. Computational analyses show that the observed CV dimer is not stable in solution, suggesting the sequential binding of two monomers. Guided by the structural analysis, we designed a set of single site substitutions, and investigated their effect on the binding of CV. Only moderate effects on the binding and the cooperativity were observed, suggesting a robustness in the interaction between CV and AChE. Taken together, we propose that the dimeric cooperative binding is due to a rare combination of chemical and structural properties of both CV and the AChE molecule itself.
|
|
| 5. |
- Atilaw, Y., et al.
(författare)
-
Four Prenylflavone Derivatives with Antiplasmodial Activities from the Stem of Tephrosia purpurea subsp leptostachya
- 2017
-
Ingår i: Molecules. - : MDPI AG. - 1420-3049 .- 1431-5157. ; 22:9
-
Tidskriftsartikel (refereegranskat)abstract
- Four new flavones with modified prenyl groups, namely (E)-5-hydroxytephrostachin (1), purleptone (2), (E)-5-hydroxyanhydrotephrostachin (3), and terpurlepflavone (4), along with seven known compounds (5-11), were isolated from the CH2Cl2/MeOH (1:1) extract of the stem of Tephrosia purpurea subsp. leptostachya, a widely used medicinal plant. Their structures were elucidated on the basis of NMR spectroscopic and mass spectrometric evidence. Some of the isolated compounds showed antiplasmodial activity against the chloroquine-sensitive D6 strains of Plasmodium falciparum, with (E)-5-hydroxytephrostachin (1) being the most active, IC50 1.7 +/- 0.1 mu M, with relatively low cytotoxicity, IC50 > 21 mu M, against four cell-lines.
|
|
| 6. |
- Atilaw, Y., et al.
(författare)
-
Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata
- 2017
-
Ingår i: Molecules. - : MDPI AG. - 1420-3049 .- 1431-5157. ; 22:2
-
Tidskriftsartikel (refereegranskat)abstract
- In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4-ethoxy-3-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.
|
|
| 7. |
- Awadalla, M. K. A., et al.
(författare)
-
Improved Homology Model of the Human all-trans Retinoic Acid Metabolizing Enzyme CYP26A1
- 2016
-
Ingår i: Molecules. - : MDPI AG. - 1420-3049 .- 1431-5157. ; 21:3
-
Tidskriftsartikel (refereegranskat)abstract
- A new CYP26A1 homology model was built based on the crystal structure of cyanobacterial CYP120A1. The model quality was examined for stereochemical accuracy, folding reliability, and absolute quality using a variety of different bioinformatics tools. Furthermore, the docking capabilities of the model were assessed by docking of the natural substrate all-trans-retinoic acid (atRA), and a group of known azole- and tetralone-based CYP26A1 inhibitors. The preferred binding pose of atRA suggests the (4S)-OH-atRA metabolite production, in agreement with recently available experimental data. The distances between the ligands and the heme group iron of the enzyme are in agreement with corresponding distances obtained for substrates and azole inhibitors for other cytochrome systems. The calculated theoretical binding energies agree with recently reported experimental data and show that the model is capable of discriminating between natural substrate, strong inhibitors (R116010 and R115866), and weak inhibitors (liarozole, fluconazole, tetralone derivatives).
|
|
| 8. |
- Baldassarre, Maurizio, et al.
(författare)
-
Simultaneous Fitting of Absorption Spectra and Their Second Derivatives for an Improved Analysis of Protein Infrared Spectra
- 2015
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 20:7, s. 12599-12622
-
Tidskriftsartikel (refereegranskat)abstract
- Infrared spectroscopy is a powerful tool in protein science due to its sensitivity to changes in secondary structure or conformation. In order to take advantage of the full power of infrared spectroscopy in structural studies of proteins, complex band contours, such as the amide I band, have to be decomposed into their main component bands, a process referred to as curve fitting. In this paper, we report on an improved curve fitting approach in which absorption spectra and second derivative spectra are fitted simultaneously. Our approach, which we name co-fitting, leads to a more reliable modelling of the experimental data because it uses more spectral information than the standard approach of fitting only the absorption spectrum. It also avoids that the fitting routine becomes trapped in local minima. We have tested the proposed approach using infrared absorption spectra of three mixed α/β proteins with different degrees of spectral overlap in the amide I region: ribonuclease A, pyruvate kinase, and aconitase.
|
|
| 9. |
- Bednarska, Joanna, et al.
(författare)
-
Nonempirical Simulations of Inhomogeneous Broadening of Electronic Transitions in Solution : Predicting Band Shapes in One- and Two-Photon Absorption Spectra of Chalcones
- 2017
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 22:10
-
Tidskriftsartikel (refereegranskat)abstract
- We have examined several approaches relying on the Polarizable Embedding (PE) scheme to predict optical band shapes for two chalcone molecules in methanol solution. The PE-TDDFT and PERI-CC2 methods were combined with molecular dynamics simulations, where the solute geometry was kept either as rigid, flexible or partly-flexible (restrained) body. The first approach, termed RBMD-PE-TDDFT, was employed to estimate the inhomogeneous broadening for subsequent convolution with the vibrationally-resolved spectra of the molecule in solution determined quantum-mechanically (QM). As demonstrated, the RBMD-PE-TDDFT/QM-PCM approach delivers accurate band widths, also reproducing their correct asymmetric shapes. Further refinement can be obtained by the estimation of the inhomogeneous broadening using the RBMD-PERI-CC2 method. On the other hand, the remaining two approaches (FBMD-PE-TDDFT and ResBMD-PE-TDDFT), which lack quantum-mechanical treatment of molecular vibrations, lead to underestimated band widths. In this study, we also proposed a simple strategy regarding the rapid selection of the exchange-correlation functional for the simulations of vibrationally-resolved one-and two-photon absorption spectra based on two easy-to-compute metrics.
|
|
| 10. |
- Behren, Sandra, et al.
(författare)
-
Glycopeptides and -Mimetics to Detect, Monitor and Inhibit Bacterial and Viral Infections : Recent Advances and Perspectives
- 2019
-
Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 24:6
-
Forskningsöversikt (refereegranskat)abstract
- The initial contact of pathogens with host cells is usually mediated by their adhesion to glycan structures present on the cell surface in order to enable infection. Furthermore, glycans play important roles in the modulation of the host immune responses to infection. Understanding the carbohydrate-pathogen interactions are of importance for the development of novel and efficient strategies to either prevent, or interfere with pathogenic infection. Synthetic glycopeptides and mimetics thereof are capable of imitating the multivalent display of carbohydrates at the cell surface, which have become an important objective of research over the last decade. Glycopeptide based constructs may function as vaccines or anti-adhesive agents that interfere with the ability of pathogens to adhere to the host cell glycans and thus possess the potential to improve or replace treatments that suffer from resistance. Additionally, synthetic glycopeptides are used as tools for epitope mapping of antibodies directed against structures present on various pathogens and have become important to improve serodiagnostic methods and to develop novel epitope-based vaccines. This review will provide an overview of the most recent advances in the synthesis and application of glycopeptides and glycopeptide mimetics exhibiting a peptide-like backbone in glycobiology.
|
|
