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A simple and sensitive label-free electrochemiluminescence (ECL) immunosensor based on the use of luminol functionalized gold nanoparticles (luminol-AuNPs) as antibody carriers and sensing platform is described for detecting the acute myocardial infarction biomarker cTnI. The ECL immunosensor was fabricated by the assembly of luminol-AuNPs conjugated with biotinylated antibodies against cTnI (biotin-anti-cTnI-luminol-AuNPs) with the streptavidin coated AuNPs (SA-AuNPs) modified Au electrode directly by virtue of the biotin-SA system. The fabricated sensing platform exhibited stable and strong ECL intensity and could be used for the recognition of target antigen. In the presence of cTnI, a decrease in the ECL intensity was observed. Direct detection of the ECL signal changes during antigen-antibody immunoreactions can be used for the quantification of cTnI. The ECL response exhibited a quite wide dynamic range from 1000 ng mL(-1) down to 0.1 ng mL(-1). The proposed method has been successfully applied in the detection of cTnI in real plasma samples. This protocol is simple, fast, sensitive, specific, stable and reliable. This work reveals that the luminol-AuNPs are excellent sensing platforms for the fabrication of simple and sensitive immunosensors. Moreover, the proposed strategy may also be extended for the detection of other biomarkers, which is of great application potential in clinical and pharmaceutical analysis.

Molecular dynamics simulations are performed to investigate the dynamic properties of wild-type HIV-1 protease and its two multi-drug-resistant variants (Flap + (L10I/G48V/I54V/V82A) and Act (V82T/I84V)) as well as their binding with APV and DRV inhibitors. The hydrophobic interactions between flap and 80 s (80’s) loop residues (mainly I50-I84’ and I50’-I84) play an important role in maintaining the closed conformation of HIV-1 protease. The double mutation in Act variant weakens the hydrophobic interactions, leading to the transition from closed to semi-open conformation of apo Act. APV or DRV binds with HIV-1 protease via both hydrophobic and hydrogen bonding interactions. The hydrophobic interactions from the inhibitor is aimed to the residues of I50 (I50’), I84 (I84’), and V82 (V82’) which create hydrophobic core clusters to further stabilize the closed conformation of flaps, and the hydrogen bonding interactions are mainly focused with the active site of HIV-1 protease. The combined change in the two kinds of protease-inhibitor interactions is correlated with the observed resistance mutations. The present study sheds light on the microscopic mechanism underlying the mutation effects on the dynamics of HIV-1 protease and the inhibition by APV and DRV, providing useful information to the design of more potent and effective HIV-1 protease inhibitors.

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A metal-free oxidation system employingtert-butyl hydroperoxide (TBHP) has been developed for selective oxidation of structurally diverse benzylic sp3C–H bonds.

Protein folding is subject to the effects of solvation environment. A variety of organic solvents are used as additives for in vitro refolding of denatured proteins. Examination of the solvent effects on protein folding could be of fundamental importance to understand the molecular interactions in determining protein structure. This article investigated the folding of α-helix and β-hairpin structures in water and the solutions of two representative refolding additives (methanol (MeOH) and 1-Ethyl-3-methylimidazolium chloride (EMIM-Cl) ionic liquid) using REMD simulations. For both α-helix and β-hairpin in MeOH/water solution or α-helix in EMIM-Cl/water solution, the transient structures along the folding pathway are consistent with the counterparts in water but the relative statistical weights are changed, leading to the decrease in the overall folding free energy barrier. Accordingly, MeOH promotes the folding of both α-helix and β-hairpin but EMIM-Cl ionic liquid only promotes the folding of α-helix, consistent with experimental observations. The present study reveals for the first time the trivial effects on folding route but significant effects on folding thermodynamics from MeOH and EMIM-Cl, explaining the function of protein refolding additives and testifying the validity of the folding mechanism revealed by in vitro protein folding study using refolding additives.

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality all over the world and multidrug resistance TB (MDR-TB) pose a serious threat to the TB control and represent an increasing public health problem. In this work, we report a homogeneous signal-on electrochemiluminescence (ECL) DNA sensor for the sensitive and specific detection of rpoB genes of MDR-TB by using ruthenium(II) complex functionalized graphene oxide (Ru-GO) as suspension sensing interface and ferrocene-labeled ssDNA (Fc-ssDNA) as ECL intensity controller. The ECL of Ru-GO could be effectively quenched by Fc-ssDNA absorbed on the Ru-GO nanosheets. The Ru-GO has good discrimination ability over ssDNA and dsDNA. Mutant ssDNA target responsible for the drug resistant tuberculosis can hybridize with Fc-ssDNA and release Fc-ssDNA from Ru-GO surface, leading to the recovery of ECL. Mutant ssDNA target can be detected in a range from 0.1 to 100 nM with a detection limit of 0.04 nM. The proposed protocol is sensitive, specific, simple, time-saving and polymerase chain reaction free without complicated immobilization, separation and washing steps, which creates a simple but valuable tool for facilitating fast and accurate detection of disease related specific sequences or gene mutations.

The study provided an integrated view of the transition pathway of the flap opening of HIV-1 protease using MD simulation.