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1.
Front Neurosci ; 18: 1323741, 2024.
Article in English | MEDLINE | ID: mdl-38426022

ABSTRACT

Background: Earlier neuroimaging investigations showed that abnormal brain activity in patients with alcohol use disorder (AUD) was frequency dependent. However, there is lacking of a comprehensive method to capture the amplitude of multi-frequency bands directly. Here, we used a new method, the power spectrum slope (PSS) to explore abnormal spontaneous activity of brain in patients with AUD. Methods: Thirty-three AUD patients and 29 healthy controls (HCs) enrolled in this study. The coefficient b and the power-law slope b' were calculated and compared between two groups. We also used the receiver operating characteristic (ROC) curve to examine the ability of the PSS analysis to distinguish between AUD and HCs. We next examined the correlation between PSS difference in the brain areas and the severity of alcohol dependence. Results: Thirty AUD patients and 26 HCs were retained after head motion correction. The two metrics of PSS values increased in the left precentral gyrus in AUD patients. The area under the curve values of PSS differences in the specific brain area were respectively 0.836 and 0.844, with sensitivities of 86.7% and 83.3% and specificities of 73.1% and 76.9%. The Michigan Alcoholism Screening Test (MAST) and Alcohol drinking scale (ADS) scores were not significantly correlated with the PSS values in the specific brain area. Conclusion: As a novel method, the PSS can well detect abnormal local brain activity in the AUD patients and may offer new insights for future fMRI studies.

2.
Zootaxa ; 5403(4): 447-458, 2024 Jan 23.
Article in English | MEDLINE | ID: mdl-38480425

ABSTRACT

The taxonomy of the genus Telostholus (Hymenoptera: Pompilidae: Pompilinae) from China is studied and one species is newly described and illustrated: T. venarectus Song & Ma, sp. nov. Additionally, two species, T. lao and T. malayensis are newly reported from China. A key to the world species of Telostholus is provided.


Subject(s)
Hymenoptera , Wasps , Animals , China
3.
BMC Psychiatry ; 23(1): 894, 2023 11 30.
Article in English | MEDLINE | ID: mdl-38037006

ABSTRACT

BACKGROUND: Alcohol use disorder (AUD) has a negative impact on one's health and wastes a lot of societal resources since it damages one's brain tissue. Yet the knowledge of the neural mechanisms underlying alcohol addiction still remains limited. This study aims to investigate the neural mechanisms underlying alcohol addiction by using voxel-wise binarized degree centrality (DC), weighted DC and functional connectivity (FC) methods to analyze brain network activity in individuals with AUD. METHODS: Thirty-three AUD patients and 29 healthy controls (HC) participated in this study. Binarized and weighted DC approach coupled with a second seed-based FC algorithm was used to assess the abnormal intrinsic hub features in AUD. We also examined the correlation between changes in functional network nodes and the severity of alcohol dependence. RESULTS: Thirty AUD patients and 26 HC were retained after head motion correction. The spatial distribution maps of the binarized DC and weighted DC for the AUD and HC groups were roughly similar. In comparison to HC, the AUD group had decreased binarized DC and decreased weighted DC in the left precentral gyrus (PreCG) and the left inferior parietal lobule (IPL). Significantly different brain regions in the DC analysis were defined as seed points in the FC analysis. Compared with HC, changes in FC within the right inferior temporal gyrus (ITG), right middle temporal gyrus (MTG), left dorsolateral superior frontal gyrus (SFGdor), bilateral IPL, left precuneus (PCUN), left lingual gyrus (LING), right cerebellum_crus1/ITG/inferior occipital gyrus (IOG) and right superior parietal gyrus (SPG) were observed. The correlation analysis revealed that FC of right MTG-right PreCG was negatively correlated with MAST scores, and FC of right IPL-left IPL was positively correlated with ADS scores. CONCLUSIONS: Alcohol use disorder is associated with aberrant regional activities in multiple brain areas. Binarized DC, weighted DC and FC analyses may be useful biological indicators for the detection of regional brain activities in patients with AUD. Intergroup differences in FC have also been observed in AUD patients, and these variations were connected to the severity of the symptoms. The AUD patients with lower FC value of the right IPL - left IPL has a lighter dependence on alcohol. This difference in symptom severity may be a compensation for cognitive impairment, indicating a difference in pathological pathways. Future AUD research will now have a fresh path thanks to these discoveries.


Subject(s)
Alcoholism , Humans , Alcoholism/diagnostic imaging , Brain Mapping/methods , Magnetic Resonance Imaging/methods , Brain/diagnostic imaging , Parietal Lobe/diagnostic imaging
4.
Ear Nose Throat J ; 101(7): 435-442, 2022 Aug.
Article in English | MEDLINE | ID: mdl-32627620

ABSTRACT

OBJECTIVE: This study aimed to investigate and analyze the anatomic characteristics of the retromaxillary cell (RMC) by using computed tomography (CT) images of paranasal sinuses and to improve its identification with ethmomaxillary sinus (EMS). METHODS: The paranasal sinus CT scans of 441 outpatients or inpatients in our hospital from January 2018 to October 2018 were analyzed. The incidence of RMC, EMS, Haller cell, imaging anatomical characteristics, and morphological manifestations were observed via sinus CTs. The relationship of RMC and ipsilateral maxillary sinusitis was analyzed. RESULTS: The incidence of RMC is 83.90% (740/882). The incidence of males and females was 83.81% (414/494) and 84.02% (326/388), respectively. The incidence of bilateral (72.79%, 321/441) was much higher than that of unilateral (22.22%, 98/441). The lateral extension of the RMC ranged from 1.18 to 13.31 mm, with an average of 6.10 ± 2.03 mm. The incidence of ipsilateral maxillary sinus opacification on the RMC sides and non-RMC sides has no significance difference (χ2 = .054, P = .459). The incidence of Haller cell and EMS decreased significantly in the presence of RMC (P < .01). CONCLUSION: The RMC is an anatomical variation originating from posterior ethmoid cells, which is commonly encountered in the clinic. The pneumatization of RMC is highly variable, and a bilateral is common. During endoscopic sinus surgery, it is necessary to carefully identify such an air cell to ensure the complete opening of the paranasal sinus during surgery.


Subject(s)
Maxillary Sinusitis , Paranasal Sinuses , Ethmoid Bone , Female , Head , Humans , Male , Maxillary Sinus/diagnostic imaging , Paranasal Sinuses/anatomy & histology , Paranasal Sinuses/diagnostic imaging , Tomography, X-Ray Computed
5.
Acta Radiol ; 62(2): 251-259, 2021 Feb.
Article in English | MEDLINE | ID: mdl-32423229

ABSTRACT

BACKGROUND: Patients with alcohol-use disorder (AUD) demonstrate dysfunctional cerebral network connectivity. However, limited studies have investigated attention systems in AUD. PURPOSE: To assess functional (FC) and effective connectivity (EC) in the dorsal (DAN) and ventral attention networks (VAN) and default mode network (DMN) in patients with AUD using resting-state functional magnetic resonance imaging (rs-fMRI). MATERIAL AND METHODS: MRI and rs-fMRI data were obtained from 28 men with AUD and 30 age-matched healthy controls. Independent component analysis was used to identify and extract network data, for comparison between the two groups. Effective connectivity was evaluated using Granger causality analysis (GCA) by selecting significantly different brain areas as regions of interest (ROI). Signed-path coefficients between ROIs were computed in bivariate mode. RESULTS: In patients with AUD, FC decreased in the left superior parietal gurus (SPG) and left interparietal sulcus (IPS, in DAN); FC decreased in the right superior frontal gyrus (SPG) and right middle frontal gyrus (MFG, in DMN). GCA values indicated that the DMN exerts a positive causal effect on the DAN (P = 0.007/0.027), which consequently exerts a negative causal effect on the DMN (P = 0.032). Signed-path coefficients from the right MFG to the left IPS correlated negatively with MAST scores (P = 0.015). CONCLUSION: We found novel inter-network connectivity dysfunction in patients with AUD, which indicates abnormal causal relations between resting-state DAN and DMN. Thus, patients with AUD may have abnormal top-down attention modulation and cognition.


Subject(s)
Alcoholism/physiopathology , Brain/diagnostic imaging , Brain/physiopathology , Default Mode Network/diagnostic imaging , Default Mode Network/physiopathology , Magnetic Resonance Imaging/methods , Adult , Alcoholism/diagnosis , Attention , Brain Mapping/methods , Humans , Male , Middle Aged
6.
J Am Chem Soc ; 142(47): 20021-20029, 2020 11 25.
Article in English | MEDLINE | ID: mdl-33180475

ABSTRACT

An efficient synthesis of nucleoside 5'-monothiophosphates under mild reaction conditions using commercially available thiophosphoryl chloride was achieved with a cinchona alkaloid catalyst. A detailed mechanistic study of the reaction was undertaken, employing a combination of reaction kinetics, NMR spectroscopy, and computational modeling, to better understand the observed reactivity. Taken collectively, the results support an unprecedented mechanism for this class of organocatalyst.

7.
Org Biomol Chem ; 17(31): 7315-7319, 2019 08 07.
Article in English | MEDLINE | ID: mdl-31342046

ABSTRACT

This protocol provides a novel, environmentally friendly and simple method for the synthesis of (Z)-tetrahydrothiophene derivatives using the nucleophilic thiyl radical intramolecular cycloaddition cascade process to construct C-S bonds under transition-metal-free conditions. This transformation process offers a broad substrate scope, good functional group tolerance, and excellent stereoselectivity (Z/E ratios up to 99/1). Moreover, the process uses odourless, stable and cheap EtOCS2K as the sulfur source.

8.
J Mater Chem B ; 4(23): 4198-4205, 2016 Jun 21.
Article in English | MEDLINE | ID: mdl-32264622

ABSTRACT

Infected bone defects are normally regarded as contraindications for bone repair. In the present study, a hollow mesoporous structure of silica (SiO2) microspheres was first synthesized and loaded with ibuprofen (IBU). Poly(1,8-octanediol-co-citrate) (POC) and ß-tricalcium phosphate (ß-Ca3(PO4)2, ß-TCP), together with IBU-loaded SiO2 were fabricated by a 3D printing technique based on the Freeform Fabrication System with Micro-Droplet Jetting (FFS-MDJ). The physiochemical properties, compressive modulus, drug release behavior, antimicrobial properties and cell response of the composite scaffold were systematically investigated. The developed IBU-loaded SiO2/ß-TCP/POC scaffolds presented a highly interconnected porous network, macropores (350-450 µm) and mesopores (3.65 nm), as well as proper compressive modulus and biocompatibility. The addition of hollow SiO2 microspheres was found to decrease the burst release and increase the cumulative release amount of IBU. In addition, IBU-loaded SiO2/ß-TCP/POC showed a long-term effect on inhibiting E. coli growth by agar diffusion. The result indicated that the IBU-loaded SiO2/ß-TCP/POC scaffold, with a hierarchically macro/mesoporous, highly interconnected pore structure and an effective antimicrobial property, demonstrates promise for bone regeneration in the clinical case of infected bone defects.

9.
J Mater Chem B ; 3(47): 9173-9181, 2015 Dec 21.
Article in English | MEDLINE | ID: mdl-32263132

ABSTRACT

The development of injectable calcium phosphate cements (ICPC) represents a promising approach for minimally invasive surgical techniques. However, the undesirable anti-washout property and slow setting time of ICPC greatly hinder its clinical application. Xanthan gum (XG) has strong hydrophilic, shape retention and rheological properties. In this study, a fast setting and anti-washout injectable calcium-magnesium phosphate cement (fa-ICMPC) was developed by introducing XG, as an anti-washout agent, and magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The bone-regenerative capacity and the bioresorption of the fa-ICMPC were also investigated by injecting it directly into a rabbit thigh bone defect. The result showed that XG imparted anti-washout properties to the fa-ICMPC and enhanced the injectability of the fa-ICMPC. With the protection of thick viscous films formed by XG, the setting of the fa-ICMPC was not disturbed but accelerated due to the synergistic effect of MPC. The result demonstrated that fa-ICMPC was not crumbled and could fill the defects tightly. The newly-formed bone tissue grew into fa-ICMPC along with the degradation of the materials. In short, the fa-ICMPC exhibited potent anti-washout properties, fast setting, improved injectability, good biodegradability and osteoconductivity, and has the potential to repair bone defects by minimal invasive treatment.

10.
Bioresour Technol ; 139: 107-12, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23648759

ABSTRACT

The base (such as CaO)-catalyzed heterogeneous preparation of biodiesel encounters a number of obstacles including the need for CaO pretreatment and the reactions being incomplete (typically 90-95% yields). In this study, a number of glymes were investigated as benign solvents for the CaO-catalyzed transesterification of soybean oil into biodiesel with a high substrate loading (typically soybean oil >50% v/v). The triglyceride-dissolving capability of glymes led to a much faster reaction rate (>98% conversions in 4h) than in methanol alone (typically 24h) and minimized the saponification reaction when catalyzed by anhydrous CaO or commercial lime without pre-activation. The use of glyme (e.g. P2) as co-solvent also activates commercial lime to become an effective catalyst without calcination pretreatment. The SEM images suggest a dissolution-agglomeration process of CaO surface in the presence of P2, which could remove the CaCO3 and Ca(OH)2 layer coated on the surface of lime.


Subject(s)
Biofuels/analysis , Calcium Compounds/chemistry , Oxides/chemistry , Solvents/chemistry , Soybean Oil/chemistry , Catalysis , Esterification , Methanol/chemistry , Microscopy, Electron, Scanning , Temperature
11.
J Enzyme Inhib Med Chem ; 27(5): 715-21, 2012 Oct.
Article in English | MEDLINE | ID: mdl-21985312

ABSTRACT

Betulinic acid is a natural product possessing abundant and favourable biological activity, including anti-cancer, anti-malarial, anti-inflammatory and anti-HIV properties, while causing minimal toxicity to unaffected cells. The full biological potency of betulinic acid cannot be fully unlocked, however, for a number of reasons, a primary one being its limited solubility in aqueous and biologically pertinent organic media. Aiming to improve the water solubility of betulinic acid without disrupting its structurally related bioactivity, we have prepared different ionic derivatives of betulinic acid. Inhibition bioassays on HIV-1 protease-catalysed peptide hydrolysis indicate significantly improved performance resulting from converting the betulinic acid to organic salt form. Indeed, for one particular cholinium-based derivative, its water solubility is improved more than 100 times and the half maximal inhibitory concentration (IC(50)) value (22 µg mL(-1)) was one-third that of wide-type betulinic acid (60 µg mL(-1)). These encouraging results advise that additional studies of ionic betulinic acid derivatives as a therapeutic solution against HIV-1 infection are warranted.


Subject(s)
HIV Protease Inhibitors/pharmacology , HIV Protease/drug effects , Triterpenes/pharmacology , Catalysis , Glycine/chemistry , HIV Protease Inhibitors/chemistry , Hydrolysis , Ions , Magnetic Resonance Spectroscopy , Pentacyclic Triterpenes , Solubility , Triterpenes/chemistry , Betulinic Acid
12.
Ga J Sci ; 69(2-3): 89-101, 2011.
Article in English | MEDLINE | ID: mdl-23564988

ABSTRACT

Porphyrins are a group of tetrapyrrole pigments. Physical and chemical properties of porphyrins are often related to their compositions and structures. We conducted 1H solution NMR and UV-visible spectral analysis to characterize the structural feature of a water-soluble, synthetic porphyrin i.e. tetrakis (p-sulfonatophenyl) porphyrin, TPPS4, and its interaction with different metal ions in aqueous solutions. The results indicate that tetrapyrrole and tetraphenyl rings in TPPS4 molecule form a co-planar electron conjugation system; transition-metal ions show stronger binding capacity than alkali and alkali-earth metal ions; the relative stabilities of TPPS4-metal ion complexes can be well assessed by NMR and UV-visible spectral data.

13.
Biotechnol Lett ; 32(8): 1109-16, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20364294

ABSTRACT

Three new ether-functionalized hydrophobic ionic liquids (ILs) were synthesized. Two proteases (subtilisin and alpha-chymotrypsin both covalently immobilized on chitosan) exhibited high synthetic activity (1-3 micromol/min x g) and selectivity (>97-99%, esterification over hydrolysis) in these ILs containing 10-15% (v/v) water during the transesterification of N-acetyl-L-phenylalanine ethyl ester with 1-propanol. However, the same reaction in t-butanol or [BMIM][Tf(2)N], with water contents higher than 2% (v/v) yielded low synthetic activities (0.2-1 micromol/min g in t-butanol) and/or poor selectivity (<40%). The high synthetic activities of proteases in ether-functionalized ILs at high water contents are explained by two reasons: (1) the hydrogen-bond donors in ILs (R(1)-O-R(2)) and chitosan (-OH) controlling the thermodynamic water activity of the reaction system, and (2) the protective role of the ether chain in reducing the cation-protein interaction.


Subject(s)
Enzymes, Immobilized/metabolism , Ethers/chemistry , Ionic Liquids/chemistry , Peptide Hydrolases/metabolism , Chymotrypsin/chemistry , Esterification , Hydrophobic and Hydrophilic Interactions , Molecular Structure , Subtilisin/chemistry , Viscosity
14.
Magn Reson Chem ; 48(2): 123-8, 2010 Feb.
Article in English | MEDLINE | ID: mdl-19960498

ABSTRACT

Interaction of polyamines with nucleotides plays a key role in many biological processes. Here we use multiple NMR techniques to characterize interaction of spermidine with adenosine 5'-triphosphate (ATP). Two-dimensional (1)H-(15)N spectra obtained from gs-HMBC experiments at varied pH show significant shift of N-1 peak around pH 2.0-7.0 range, suggesting that spermidine binds to N-1 site of ATP base. The binding facilitates N-1 deprotonation, shifting its pK(a) from 4.3 to 3.4. By correlating (15)N and (31)P chemical shift data, it is clear that spermidine is capable of concurrently binding to ATP base and phosphate sites around pH 4.0-7.0. The self-diffusion constants derived from (1)H PFG-diffusion measurements provide evidence that binding of spermidine to ATP is in 1:1 ratio, and pH variations do not induce significant nucleotide self-association in our samples. (31)P spectral analysis suggests that at neutral pH, Mg(2+) ion competes with spermidine and shows stronger binding to ATP phosphates. From (31)P kinetic measurements of myosin-catalyzed ATP hydrolysis, it is found that binding of spermidine affects the stability and reactivity of ATP. These NMR results are important for advancing the studies on nucleotide-polyamine interaction and its impact on nucleotide structures and activities under varied conditions.


Subject(s)
Adenosine Triphosphate/metabolism , Magnetic Resonance Spectroscopy/methods , Spermidine/metabolism , Adenosine Triphosphate/chemistry , Binding Sites , Catalysis , Cations, Divalent , Hydrogen-Ion Concentration , Hydrolysis , Isotope Labeling , Kinetics , Magnesium/chemistry , Myosins/chemistry , Myosins/metabolism , Nitrogen Isotopes , Phosphorus Isotopes , Spermidine/chemistry
15.
Appl Biochem Biotechnol ; 162(1): 13-23, 2010 Sep.
Article in English | MEDLINE | ID: mdl-19633977

ABSTRACT

Ionic liquids (ILs) are being explored as solvents for the enzymatic methanolysis of triglycerides. However, most available ILs (especially hydrophobic ones) have poor capability in dissolving lipids, while hydrophilic ILs tend to cause enzyme inactivation. Recently, we synthesized a new type of ether-functionalized ionic liquids (ILs) carrying anions of acetate or formate; they are capable of dissolving a variety of substrates and are also lipase-compatible (Green Chem., 2008, 10, 696-705). In the present study, we carried out the lipase-catalyzed transesterifications of Miglyol oil 812 and soybean oil in these novel ILs. These ILs are capable of dissolving oils at the reaction temperature (50 degrees C); meanwhile, lipases maintained high catalytic activities in these media even in high concentrations of methanol (up to 50% v/v). High conversions of Miglyol oil were observed in mixtures of IL and methanol (70/30, v/v) when the reaction was catalyzed by a variety of lipases and different enzyme preparations (free and immobilized), especially with the use of two alkylammonium ILs 2 and 3. The preliminary study on the transesterification of soybean oil in IL/methanol mixtures further confirms the potential of using oil-dissolving and lipase-stabilizing ILs in the efficient production of biodiesels.


Subject(s)
Biocatalysis , Biofuels , Ether/chemistry , Ionic Liquids/chemistry , Lipase/metabolism , Animals , Chromatography, High Pressure Liquid , Esterification , Methanol/chemistry , Soybean Oil/chemistry
16.
Anal Bioanal Chem ; 395(5): 1453-9, 2009 Nov.
Article in English | MEDLINE | ID: mdl-19756531

ABSTRACT

We conducted (31)P NMR kinetic studies and (1)H-diffusion measurements on myosin-catalyzed hydrolysis of adenosine triphosphate (ATP) under varied conditions. The data elucidate well the overall hydrolysis rate and various factors that significantly impact the reaction. We found that the enzymatic hydrolysis of ATP to adenosine diphosphate (ADP) was followed by ADP hydrolysis, and different nucleotides such as ADP and guanosine triphosphate acted as competitors of ATP. Increasing ATP or Mg(2+) concentration resulted in decreased hydrolysis rate, and such effect can be related to the decrease of ATP diffusion constants. Below 50 degrees C, the hydrolysis was accelerated by increasing temperature following the Arrhenius' law, but the hydrolysis rate was significantly lowered at higher temperature (approximately 60 degrees C), due to the thermal-denaturation of myosin. The optimal pH range was around pH 6-8. These results are important for characterization of myosin-catalyzed ATP hydrolysis, and the method is also applicable to other enzymatic nucleotide reactions.


Subject(s)
Adenosine Triphosphate/analysis , Biocatalysis , Diffusion , Magnetic Resonance Spectroscopy/methods , Myosins/metabolism , Adenosine Triphosphate/metabolism , Hydrogen-Ion Concentration , Hydrolysis , Kinetics , Magnesium/metabolism , Phosphorus Isotopes/chemistry , Protons , Temperature
17.
Zhongguo Dang Dai Er Ke Za Zhi ; 11(2): 133-7, 2009 Feb.
Article in Chinese | MEDLINE | ID: mdl-19222952

ABSTRACT

OBJECTIVE: To study the expression of signal transducer and activator of transcription 5b (STAT5b) mRNA and interleukin-4 (IL-4) mRNA in blood mononuclearcells in a rat model of asthma and the effect of montelukast (MK) and BCG-polysaccharide and nucleic acid injection (BCG-PSN) on STAT5b mRNA and IL-4 mRNA expression. METHODS: Fifty-two male Sprague-Dawley rats (weight:140-200 g) were randomly divided into four groups: asthma, MK treated and BCG-PSN-treated and control groups. Rat model of asthma was prepared by ovalbumin (OVA) sensitization. The rats were sacrificed 24 hrs after the last sensitization. Blood eosinophils (EOS) were counted. Plasma contens of IL-4 and interferon-gamma (IFN-gamma) were measured using ELISA. Expression of STAT5b mRNA and IL-4 mRNA in blood mononuclearcells was detected with SYBR GREEN I fluorescent quantitation PCR method. RESULTS: Blood contents of STAT5b mRNA and IL-4 mRNA in the untreated asthma group were significantly higher than those in the other three groups (<0.01). Blood EOS count and plasma IL-4 contents in the untreated asthma group significantly increased, while plasma IFN-gamma contents significantly decreased compared with the other three groups (<0.01). There were no significant differences in the parameters measured among the MK-treated, the BCG-PSNjtreated and the control groups. STAT5b mRNA expression was positively correlated to IL-4 mRNA expression, IL-4 content and EOS count (r=0.730,0.650, 0.664, respectively; <0.01), but negatively correlated to IFN-gamma content (r=-0.798; <0.01). CONCLUSIONS: STAT5b mRNA and IL-4 mRNA were strongly expressed in blood mononuclearcells in rats with asthma, and there was a positive correlation between them. MK and BCG-PSN had inhibitory effects on the expression of STAT5b mRNA and IL-4 mRNA, which might be contributed to suppression of airway inflammation in asthma.


Subject(s)
Acetates/pharmacology , Asthma/drug therapy , BCG Vaccine/pharmacology , Interleukin-4/genetics , Leukocytes, Mononuclear/metabolism , Quinolines/pharmacology , RNA, Messenger/blood , STAT5 Transcription Factor/genetics , Animals , Asthma/blood , Asthma/pathology , Cyclopropanes , Interferon-gamma/biosynthesis , Male , Rats , Rats, Sprague-Dawley , Sulfides
18.
Int J Mol Sci ; 9(1): 33-44, 2008 Jan.
Article in English | MEDLINE | ID: mdl-19325717

ABSTRACT

Inspired by the concept of ionic liquids (ILs), this study modified the original Mukaiyama's reagent, 2-chloro-1-methylpyridinium iodide (m.p. 200-dec), from ionic solid into liquids by changing its anion. The esterification of N-acetyl-L-phenylalanine was investigated as a model reaction. The microwave irradiation was more effective in esterifying N-acetyl-L-phenylalanine than the conventional reflux method. The original Mukaiyama's reagent was modified into ILs through manipulating its anion. However, only non-nucleophilic anions (such as EtSO(4) (-) and Tf(2)N(-)) were favorable since nucleophilic ones (such as CF(3)COO(-) and CH(3)COO(-)) could exchange with chlorine resulting in non-reactive coupling reagents. Two modified Mukaiyama's compounds (i.e. hydrophilic [2-ClMePy][EtSO(4)] and hydrophobic [2-ClMePy][Tf(2)N]) have been identified as the best ILtype coupling reagents. The esterification reaction was greatly enhanced by using 1- methylimidazole as the base instead of conventional toxic tertiary amines, and by using excess amount of alcohols as solvents instead of dichloromethane. Overall, the method reported is effective and 'greener'.

19.
Bioorg Chem ; 34(1): 15-25, 2006 Feb.
Article in English | MEDLINE | ID: mdl-16325223

ABSTRACT

This paper examined the effect of several pyridinium and imidazolium-based ionic liquids (ILs) on the protease stability in aqueous solutions. In general, the enzyme was found quite active at low concentrations of hydrophilic ILs. In aqueous environment, the enzyme was stabilized by the kosmotropic anions (such as CF3COO- and CH3COO-) and chaotropic cations (such as [BuPy]+ and [EMIM]+), but was destabilized by chaotropic anions (such as tosylate and BF4-) and kosmotropic cations (such as [BMIM]+).


Subject(s)
Aspergillus/enzymology , Imidazoles/chemistry , Peptide Hydrolases/metabolism , Pyridines/chemistry , Water/chemistry , Acetic Acid/chemistry , Enzyme Stability , Ions , Peptide Hydrolases/chemistry , Solutions/chemistry , Time Factors , Trifluoroacetic Acid/chemistry
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