APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
·
2015
·Vol. 99
·期 9
·4019-4029
·
IF 3.337
Wan Nan-Wei,Liu Zhi-Qiang,Xue Feng,Huang Kai,Tang Ling-Jiao,Zheng Yu-Guo
Halohydrin dehalogenases (HHDHs) are an important class of enzymes for preparing optically active haloalcohols, epoxides, and β-substituted alcohols. However, natural HHDHs rarely meet the requirements of industrial applications. Here, a novel high-throughput screening (HTS) methodology for directed evolution of HHDH was developed based on the colorimetric determination of azide. In this method, azide was involved in the HHDH-catalyzed ring-opening process and the decrease of azide was used to quantitatively evaluate HHDH activity. The HTS methodology was simple and sensitive (ε 460 = 1.2173 × 10 4 L mol −1 cm −1 ) and could be performed in a microplate format using whole cells. To verify the efficiency of the HTS methodology, it was adopted to engineer a HHDH (HHDH-PL) from Parvibaculum lavamentivorans DS-1, which was applied in the process for ethyl ( R )-4-cyano-3-hydroxybutanoate (HN) by the conversion of ethyl ( S )-4-chloro-3-hydroxybutanoate (( S )-CHBE)). A random mutant library containing 2500 colonies was screened using the HTS methodology, and three beneficial mutants F176M, A187R, and A187S were obtained. By combining the beneficial mutated residues, the variant F176M/A187R was identified with 2.8-fold higher catalytic efficiency for preparation of HN. The high-throughput colorimetric assay would be very useful for directed evolution of HHDH for preparing β-substituted alcohols.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
KOREAN JOURNAL OF CHEMICAL ENGINEERING
·
2016
·Vol. 33
·期 2
·610-615
·
IF 1.408
Cui Jian Dong,Liu Rong Lin,Li Lin Bo
Cross-linked enzyme aggregates from bovine pancreatic lipase were prepared by co-aggregation of lipase and BSA (Lipase-BSA-CLEAs). The main factors in the preparation of lipase-BSA-CLEAs were optimized. The highest activity recovery was around 75% under the condition of using 1% (v/v) glutaraldehyde as cross-linker and 0.05 g/L bovine serum albumin as feeder for 2 h cross linking. The optimum temperature for both lipase-CLEAs and lipase- BSA-CLEAs was measured as 60 °C, which is 10 °C higher than that of free lipase. Moreover, the lipase-BSA-CLEAs evidenced higher thermal stability and excellent reusability in comparison with the lipase-CLEAs. Lipase-BSA-CLEAs retained more than 75% of the initial activity after eight cycles of reuse, while lipase-CLEAs only retained 20% of its initial activity. Additionally, lipase-BSA-CLEAs showed more storage stability than free lipase and lipase-CLEAs. The high stability and recyclability of lipase-BSA-CLEAs make it efficient for different industrial applications.
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF NANOPARTICLE RESEARCH
·
2014
·Vol. 16
·期 8
·1-11
·
IF 2.278
Zhu Shaojia,Zhen Hong,Li Yongjun,Wang Ping,Huang Xiaoyu,Shi Ping
Graphene, a two-dimensional nanomaterial, has become a hot spot of research at the interface of nanotechnology and biomedicine. In this study, the oxidized form of graphene, graphene oxide (GO), was functionalized with 6-armed polyethylene glycol (PEG), which rendered it stable and biocompatible in physiological solution. The successful synthesis of PEGylated graphene oxide (GO-PEG) nanocarrier with low toxicity was confirmed by UV–Vis spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. By dynamic light scattering (DLS), the size distribution of the nanoparticles were shown to be 60–200 nm. Furthermore, a complex by loading an aromatic anticancer compound, podophyllotoxin (PPT), onto GO-PEG (GO-PEG/PPT) via π – π stacking and hydrophobic interactions was investigated. It was demonstrated that GO-PEG/PPT showed remarkably high cytotoxicity compared to free PPT in both the human cervical adenocarcinoma HeLa cell line and human hepatoma SMMC-7721 cell line. The loading and delivery of anticancer drugs using this kind of graphene-based nanocarrier may find potential application in biomedicine.
✓ 已验证
产品关联
DOI
高影响因子
MICROCHIMICA ACTA
·
2014
·Vol. 181
·期 15
·1981-1989
·
IF 3.719
He Linghao,Zhang Yuanchang,Liu Shunli,Fang Shaoming,Zhang Zhihong
We report on a novel graphene-based nanoarchitecture modified with plasma-polymerized propargylamine (G-PpPG) and its application in electrochemical sensors for DNA. Films of G-PpPG were characterized by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The presence of graphene enhances the electrochemical activity of the films, and the high density of amino groups (deposited at a low plasma input power) on their surface assists in the immobilization of probe DNA on the water-swollen polymeric network. By contrast, the degree of hybridization of the total complementary target DNA to the probe DNA remains unchanged when G-PpPG nanofilms prepared at higher input power. No substantial non-specific adsorption of totally mismatched target DNA on the polymer films is observed because of the complete coverage of the probe DNA. The detection limit for total complementary target DNA is approximately 1.84 nmol · L −1 . The dynamic range extends from 0.1 to 1,000 nmol · L −1 . The new nanocomposite may also be used to immobilize other probe DNA sequences, and this makes the approach potentially applicable to the detection of other oligomers.
Preparing the DNA sensor made from the graphene-based nanoarchitecture modified by using PpPG (G-PpPG) includes the following processes: (a) Modifying the Au electrode with the graphene nanosheet, (b) depositing the PpPG film onto the Au electrode coated with graphene, (c) immobilizing the probe DNA onto the G-PpPG film, and (d) hybridizing the MM0 target with the G-PpPG film immobilized with P1
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL RESEARCH IN CHINESE UNIVERSITIES
·
2014
·Vol. 30
·期 3
·362-367
·
IF 1.119
Cao Li,Jia Chunman,Zhang Qi,Chen Da,Zhang Chunyan,Qian Yaao
A fluorescent probe with a coumarin moiety bound to rhodamine 6G hydrazide( 1 ) was synthesized. Its sensing behavior toward various metal ions was investigated with fluorescence methods. Compound 1 displays different fluorescence emission responses to Al 3+ and Ca 2+ at the same excitation wavelength in the visible light region, while no changes occur after the addition of other metal ions. The binding ratios of the complexs of 1 -Al 3+ and 1 -Ca 2+ are both 2:1 according to the Job plot and high resolution mass spectrometer(HRMS) experiments. Moreover, emission spectrum of 1 -Ca 2+ complex and absorption spectrum of the rhodamine dyes overlap largely. When Al 3+ was added to the 1 -Ca 2+ system, calcium in complex 1 -Ca 2+ can be displaced by Al 3+ , resulting in the output of another ratiometric sensing signal, which demonstrates that the 1 -Ca 2+ complex can be served as a new and effective fluorescence resonance energy transfer(FRET) donor for rhodamine derivatives.
✓ 已验证
产品关联
DOI
高影响因子
COLLOID AND POLYMER SCIENCE
·
2014
·Vol. 292
·期 9
·2295-2302
·
IF 2.41
Zhang Rong-li,Sun Jia-di,Luo Jing,Xu Sheng,Liu Xiao-ya
Poly(γ-glutamic acid) (γ-PGA) has been widely used in many applications due to its excellent biodegradability, biocompatibility, and nontoxic properties. In this study, we synthesized a novel photo-sensitive amphiphilic poly(γ-glutamic acid)-graft-7-amino-4-methylcoumarin (AMC-γ-PGA) copolymer, which can self-assemble into nanoparticles (NPs) via solvent exchange method. The resultant AMC-γ-PGA NPs showed sensitivity to UV irradiation, pH, and ionic strength, owing to the presence of coumarin groups and carboxyl groups on the AMC-γ-PGA copolymer. The AMC-γ-PGA NPs were then used as a matrix to entrap hemoglobin (Hb). The obtained Hb@AMC-γ-PGA nanocomposites were cast on the electrode to form a nanocomposite film, which was then photo-crosslinked by UV irradiation to lock and immobilize Hb. Cyclic voltammetry (CV) experiment showed that the Hb@AMC-γ-PGA-nanocomposite-modified electrode exhibited good electrochemical catalytic activity for H 2 O 2 , implying that the AMC-γ-PGA NPs provided a favorable microenvironment for Hb and preserved the bioactivity of Hb. In addition, the leakage of Hb was efficiently avoided with the photo-crosslinking of the AMC-γ-PGA NPs. The biocompatible photo-sensitive AMC-γ-PGA NPs provided an excellent platform for immobilization of Hb on electrode.
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF POLYMER SCIENCE
·
2014
·Vol. 32
·期 7
·931-940
·
IF 1.42
Liu Rui-yuan,Zhang Tong,Yang Xiao-dong,Yan Yi-chen,Qu Jin-qing
A novel phenylacetylene derivative containing urea groups was synthesized and polymerized with a Rh catalyst to give the corresponding polymer, poly( 1 ) with moderate number-average molecular weights. The poly( 1 ) was soluble in toluene, CHCl 3 , CH 2 Cl 2 , THF, DMF, and DMSO, but insoluble in hexane, diethyl ether and MeOH. The specific rotation and circular dichroism (CD) spectroscopic studies revealed that poly( 1 ) took predominantly one-handed helical structures. The presence of intramolecular hydrogen bonding was confirmed by liquid-state IR spectroscopy. The helicity of poly( 1 ) could be tuned by temperature and anion. The helical conformation of the polymer was stable against Br- but susceptible to F − .
✓ 已验证
产品关联
DOI
高影响因子
Nanoscale Research Letters
·
2017
·Vol. 12
·期 1
·1-8
·
IF 2.833
Cai Limei,Yu Rufen,Hao Xi,Ding Xiangcui
In this study, novel folic acid-conjugated chitosan nanoparticle was formulated for specific delivery of bioflavonoid, Genistein (GEN), to the cervical cancer cells. The prepared GEN-loaded chitosan nanoparticles (GCN) and folic acid-conjugated GCN (FGCN) showed smaller size with a controlled drug release profile. FGCN exhibited enhanced internalization potential in HeLa cells than that of GCN. The specific internalization of FGCN was mainly due to the affinity of folic acid (FA) with FRs-α which is present in large numbers in HeLa cells. The results revealed that FGCN has a specific affinity towards HeLa cells that will contribute to the better treatment. Folic acid-tagged nanoformulations exhibited a superior cytotoxic effect compared to that of non-targeted formulations. Consistently, IC50 value of GEN decreased from 33.8 to 14.6 μg/ml when treated with FGCN after 24 h incubation. The apoptosis studies indicated that the FGCN nanoparticles were then either GCN or free GEN in terms of anticancer activity. Overall, results revealed that folate conjugation to the delivery system might have great effect on the survival of cervical cancers that will be beneficial for overall cancer treatment.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MICROCHIMICA ACTA
·
2017
·Vol. 184
·期 10
·3721-3728
·
IF 4.58
Yin Dan,Tao Yiyi,Tang Lan,Li Wei,Zhang Zhang,Li Junlong,Xie Guoming
The authors describe a dual-signal electrochemical biosensor for highly sensitive determination of the HIV-1 related gene. This method is based on the application of cascaded toehold-mediated strand displacement reactions (TMSDRs) in combination with non-enzymatic target recycling amplification (TRA). A DNA machine with two TMSDRs was designed, and this resulted in reusable target and an output of two oligonucleotides, referred to as strand A (AS) labeled with the redox tag methylene blue (MB) and as untagged strand B (BS). A ferrocene (Fc)-modified signal probe (Fc-P 1 ) is immobilized on the gold electrode surface by hybridizing with a thiolated probe (P 2 ). The labeled AS causes the dissociation of Fc molecules and the gathering of MB molecules via strand displacement reaction. The target gene triggers TMSDRs and TRA. This leads to an increase in the distance changes between the redox tags and the gold electrode. The assay works in the 1 pM to 10 nM concentration range. On account of target recycling and dual recognition, the limit of detection is as low as 0.88 pM (at an S/N ratio of 3). The assay also has a remarkable selectivity which is ascribed to the use of both cascaded TMSDRs and dual recognition. In our perception, this assay represents a robust means of wide scope in that it may be applied to the detection of various kinds of nucleic acid even in complex samples.
Schematic of a dual-signal electrochemical biosensor based on cascaded toehold-mediated strand displacement and non-enzymatic target recycling amplification strategy for the HIV-1 related gene detection. Two electroactive molecules are used to produce electrochemical signals in this “signal-on/off” sensing system.
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2017
·Vol. 28
·期 20
·15338-15344
·
IF 2.019
Tian Xinli,Yang Chuang,Si Lili,Si Gaoli
Here we report a flexible supercapacitor electrode fabricated via a simple method by applying a continuous polyaniline (PANi) coating on the surface of a cellulose nanofibers (CNFs) film. On one hand, we can recycle a large amount of bamboo fiber waste. On the other hand, we greatly improve the processing performance of PANi by making full use of CNFs’ superior mechanical properties. The flexible eco-friendly CNFs/PANi film can be directly used as an electrode without binder. SEM and FTIR measurements indicate there is a very secure combination between CNFs and PANi. The CNFs/PANi electrode boasts fine mechanical properties, excellent reversible performance and good specific capacitance (254.7 F/g at current density of 0.2 A/g). We expect the hybrid electrode will be used for flexible supercapacitor application.
✓ 已验证
产品关联
DOI
高影响因子
ANALYTICAL AND BIOANALYTICAL CHEMISTRY
·
2017
·Vol. 409
·期 16
·3993-4000
·
IF 3.431
Liu Yingxiong,Zhao Qiang
Development of simple, sensitive, and rapid method for cocaine detection is important in medicine and drug abuse monitoring. Taking advantage of fluorescence anisotropy and aptamer, this study reports a direct fluorescence anisotropy (FA) assay for cocaine by employing an aptamer probe with tetramethylrhodamine (TMR) labeled on a specific position. The binding of cocaine and the aptamer causes a structure change of the TMR-labeled aptamer, leading to changes of the interaction between labeled TMR and adjacent G bases in aptamer sequence, so FA of TMR varies with increasing of cocaine. After screening different labeling positions of the aptamer, including thymine (T) bases and terminals of the aptamer, we obtained a favorable aptamer probe with TMR labeled on the 25th base T in the sequence, which exhibited sensitive and significant FA-decreasing responses upon cocaine. Under optimized assay conditions, this TMR-labeled aptamer allowed for direct FA detection of cocaine as low as 5 μM. The maximum FA change reached about 0.086. This FA method also enabled the detection of cocaine spiked in diluted serum and urine samples, showing potential for applications.
The binding of cocaine to the TMR-labeled aptamer causes conformation change and alteration of the intramolecular interaction between TMR and bases of aptamer, leading to variance of fluorescence anisotropy (FA) of TMR, so direct FA analyis of cocaine is achieved
✓ 已验证
DOI
PubMed
高影响因子
Nanoscale Research Letters
·
2017
·Vol. 12
·期 1
·1-7
·
IF 2.833
Bo Tang,Zhengwei Wang,Huang Weiqiu,Sen Li,Tingting Ma,Haogang Yu,Xufei Li
With the development of microelectronic devices, the insufficient heat dissipation ability becomes one of the major bottlenecks for further miniaturization. Although graphene-assisted epoxy resin (ER) display promising potential to enhance the thermal performances, some limitations of the reduced graphene oxide (RGO) nanosheets and three-dimensional graphene networks (3DGNs) hinder the further improvement of the resulting thermal interface materials (TIMs). In this study, both the RGO nanosheets and 3DGNs are adopted as co-modifiers to improve the thermal conductivity of the ER. The 3DGNs provide a fast transport network for phonon, while the presence of RGO nanosheets enhances the heat transport at the interface between the graphene basal plane and the ER. The synergy of these two modifiers is achieved by selecting a proper proportion and an optimized reduction degree of the RGO nanosheets. Moreover, both the high stability of the thermal conductivity and well mechanical properties of the resulting TIM indicate the potential application prospect in the practical field.
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）