Peptide Nucleic Acid (PNA)-peptide conjugates targeting essential bacterial genes are showing promise as antisense antimicrobials in drug discovery. Optimization has focused on selection of target genes and exact localization around the ribosome binding site, but surprisingly a length optimum around 10–12 nucleobases has been found. Addressing this observation, we have investigated the relationship between PNA-length, PNA–RNA duplex stability and antimicrobial activity in E. coli in more detail. For PNAs of identical length of ten nucleobases the expected reverse correlation between the thermal stability (Tm) of the PNA–RNA duplex and the MIC for single mismatched PNAs was found. Also the expected direct correlation between the length of the PNA and the PNA–RNA duplex stability was found. Nonetheless, 10-mer PNAs [in a 6–18 mer extension series of (KFF) 3 K- and (RXR) 4 conjugates] were the most active as antisense antimicrobials in both wild type E. coli MG1655 and AS19, suggesting that the size constraint is related to the bacterial uptake of PNA-peptide conjugates. This conclusion was supported by flow cytometry data showing higher bacterial uptake of shorter PNA fluorophore labeled conjugates. Interestingly, the size-limited uptake seems independent on outer membrane integrity (AS19), and thus the results suggest that the inner membrane limits the molecular size for peptide-PNA passage.

Dopamine is an important neurotransmitter in mammalian central and peripheral nervous systems and is also a medicament to cure some neuropsychosis. In this work, ion transfer (IT), facilitated ion transfer (FIT) of protonated dopamine, and electron transfer (ET) between dopamine and ferrocene are investigated at the water/1,2-dichloroethane (W/DCE) interface. The IT and FIT reactions of protonated dopamine can be observed simultaneously within the same potential window. The experimental results demonstrate that dibenzo-18-crown-6, dibenzo-24-crown-8, and benzo-15-crown-5 work well with the protonated dopamine. The amperometric detection of dopamine based on either the IT or the FIT of protonated dopamine can get rid of the interference of ascorbic acid, and the lowest concentration that can be determined is approximately 0.05 microM by differential pulse voltammetry. For the ET reaction, its kinetics can be evaluated by scanning electrochemical microscopy, and the results show that the relationship between rate constants and driving force at the unmodified W/DCE interface obeys the Butler-Volmer equation in a rather wide potential region. When the W/DCE interface is modified by egg lecithin, the ET rate constants decrease with increasing concentration of egg lecithin, which indicates that egg lecithin hinders the ET reaction. When the driving force is increased to a certain degree, the linear relationship between ET rate constants and the driving force is distorted. These results will be helpful to understand both the pharmacodynamics and the neural signal transmission mechanism of dopamine at biological membranes and also provide a novel way to detect dopamine.

The capacitance of monolayer-protected gold nanoclusters (MPCs), C MPC , in solution has been theoretically reconsidered from an electrostatic viewpoint, in which an MPC is considered as an isolated charged sphere within two dielectric layers, the intrinsic coating monolayer, and the bulk solvent. The model predicts that the bulk solvent provides an important contribution to C MPC and influences the redox properties of MPCs. This theoretical prediction is then examined experimentally by comparing the redox properties of MPCs in four organic solvents: 1,2-dichloroethane (DCE), dichloromethane (DCM), chlorobenzene (CB), and toluene (TOL), in all of which MPCs have excellent solubility. Furthermore, this set of organic solvents features a dielectric constant in a range from 10.37 (DCE) to 2.38 (TOL), which is wide enough to probe the solvent effect. In these organic solvents, tetrahexylammonium bis(trifluoromethylsulfonyl)imide (THATf 2 N) is used as the supporting electrolyte. Cyclic and differential pulse voltammetric results provide concrete evidence that, despite the monolayer protection, the solvent plays a significant effect on the properties of MPCs in solution.

Fingerprint analysis is one of the most important methods used for personal identification of evidence found at a crime scene for forensic purposes. Using scanning electrochemical microscopy (SECM) imaging, researchers can visualize the ultrastructure of human fingerprints on wet porous and non-porous surfaces by combining with silver-staining or multi-metal-deposition (MMD) technology. SECM allows investigators to image chemical activities of fingerprint surfaces with an impressively high resolution, such as the third level valuable information for confirming an identification. This methodology takes a significant advantage of the high sensitivity of SECM towards the small variation of electrochemical reaction rates at the substrate surface. In this review, we highlight the recent breakthroughs in ultrasensitive imaging and detection of latent fingerprints with a special focus on a novel application of SECM. We will also discuss our perspectives on future research directions.

Fragile X syndrome is caused by the inactivation of the X-linked FMR1 gene, leading to the loss of its encoded protein FMRP. Although macroorchidism and defects in neuronal architecture and function have been associated with lack of FMRP, the exact molecular mechanism underlying this disease remains unclear. We have reported previously that in the brain and testis of mice, FMRP specifically interacts with a distinct mRNA nuclear export factor NXF2 but not with its close relative NXF1, a ubiquitously expressed essential mRNA nuclear export factor. This interaction marked NXF2 as a putative functional partner of FMRP. Here, we demonstrate by immunoprecipitation and quantitative real-time RT-PCR that, in cultured mouse neuronal cells, both FMRP and NXF2 are present in Nxf1 mRNA-containing ribonucleoprotein particles. Further, we show that expression of NXF2 leads to the destabilization of Nxf1 mRNA and that this effect is abolished when Fmr1 expression is reduced by siRNA, arguing that both proteins collaborate to exert this effect. Importantly, these findings correlate well with our observations that in both mouse hippocampal neurons and male germ cells where the expression of FMRP and NXF2 is most prominent, the expression of NXF1 is relatively poorly expressed. Our studies thus identify Nxf1 mRNA as a likely biologically relevant in vivo target of both FMRP and NXF2 and implicate FMRP, in conjunction with NXF2, as a posttranscriptional regulator of a major mRNA export factor. Such regulation may prove important in the normal development and function of neurons as well as of male germ cells.germ cell ͉ neuron ͉ RNA stability

Scanning electrochemical microscopy was used to probe the influence of a driving force on the heterogeneous electron transfer (ET) processes at the externally polarized water/1,2-dichloroethane interface. Being a part of the driving force, the Galvani potential difference at the interface, Deltaowphi, can be quantitatively controlled in a wide range, allowing the precise measurements of the rate constants of the ET reactions. Two opposite systems were chosen in this work. One was 5,10,15,20-tetraphenyl 21H,23H-porphyrin zinc (ZnPor, O)/Fe(CN)64- (W), and the other was TCNQ (O)/Fe(CN)63- (W). For both systems studied, the relations between the rate constant and the Deltaowphi were of parabolic shape; that is, the rate constants increased initially with the Deltaowphi until reaching a maximum and then decreased steadily as the Deltaowphi increased further. This is in accordance with the prediction of the Marcus theory. To our knowledge, this is the first report that the Marcus inverted region can be observed electrochemically at an unmodified liquid/liquid interface with only one redox couple at each phase. The effect of the concentrations of the organic supporting electrolyte has also been discussed in detail.

Sharp practice: A water/n‐octanol interface can be formed at the tip of a very short and sharp nanopipette, and can be polarized externally (see picture). This interface has been used to investigate various ion‐transfer processes and evaluate partition coefficients for ionizable species.

A simple method termed immunological multimetal deposition (iMMD) was developed for rapid visualization of sweat fingerprints with bare eyes, by combining the conventional MMD with the immunoassay technique. In this approach, antibody-conjugated gold nanoparticles (AuNPs) were used to specifically interact with the corresponding antigens in the fingerprint residue. The AuNPs serve as the nucleation sites for autometallographic deposition of silver particles from the silver staining solution, generating a dark ridge pattern for visual detection. Using fingerprints inked with human immunoglobulin G (hIgG), we obtained the optimal formulation of iMMD, which was then successfully applied to visualize sweat fingerprints through the detection of two secreted polypeptides, epidermal growth factor and lysozyme. In comparison with the conventional MMD, iMMD is faster and can provide additional information than just identification. Moreover, iMMD is facile and does not need expensive instruments.