UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 2: selected applications

Electrical detection of pathogenic bacteria in food samples using information visualization methods with a sensor based on magnetic nanoparticles functionalized with antimicrobial peptides

Outbreaks of foodborne diseases demand simple, rapid techniques for detecting pathogenic bacteria beyond the standard methods that are not applicable to routine analysis in the food industry and in the points of food consumption. In this work, we developed a sensitive, rapid and low-cost assay for detecting Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhi) in potable water and apple juice. The assay is based on electrical impedance spectroscopy measurements with screen-printed interdigitated electrodes coupled with magnetite nanoparticles functionalized with the antimicrobial peptide melittin (MLT). The data were analyzed with the information visualization methods Sammon's Mapping and Interactive Document Map to distinguish samples at two levels of contamination from food suitable for consumption. With this approach it has been possible to detect E. coli concentration down to 1 CFU mL^-1 in potable water and 3.5 CFU mL^-1 in apple juice without sample preparation, within only 25 min. This approach may serve as a low-cost, quick screening procedure to detect bacteria-related food poisoning, especially if the impedance data of several sensing units are combined.

Probing the Gelatin-Alkylammonium Salt Mixed Assemblies through Surface Tensiometry and Fluorimetry

The interactions, nature of the organization, and physicochemical properties of alkyltrimethylammonium bromide (C _nTAB, n = 12, 14, and 16)-gelatin mixed assemblies were investigated by UV-visible spectrometry, surface tensiometry, and fluorimetry techniques. The synergistic interaction between the surfactant and gelatin was established from the decrease in critical micellar concentration (cmc) and the increase in molecular parking area of surfactants with an increase in percentage of gelatin from 0 to 0.4%; for example, the cmc of C₁₆TAB decreased from 0.93 mM in water to 0.44 mM in the presence of 0.4% gelatin, whereas its A_min increased from 134.98 to 325.55 Ų. The fluorescence anisotropy data and polarity parameters of pyrene indicated the progressive change in the anisotropy and micropolarity of the mixed system media with gelatin percentage, respectively. The decrease in aggregation number with an increase in gelatin concentration can be attributed to the enhanced compatibility of surfactants with the bulk microenvironment. The maximum rigidity of the mixed system was also significant from the lifetime data of tyrosine. The formation of Menger micelles on gelatin segments was supported by surface tension and anisotropy data. The overall observations can be attributed to the formation of micelles via gelatin-surfactant aggregates; gelatin segments are localized within the microdomain of these aggregates.

Near-Infrared Fluorescent Dye-Decorated Nanocages to Form Grenade-like Nanoparticles with Dual Control Release for Photothermal Theranostics and Chemotherapy

Recently, nanoparticles (NPs) have been widely investigated for delivery of anticancer drugs. Here, a dual control drug-release modality was developed that uses naturally occurring protein apoferritin loaded with doxorubicin (DOX) and ADS-780 near-infrared (NIR) fluorescent dye-decorated NPs (ADNIR NPs). ADNIR NPs act as a grenade to detonate the targeted tumor site following laser irradiation (photothermal therapy, PTT) and explode into cluster warheads (apoferritin-loaded DOX nanocages, AF-DOX NCs) that further destroy the tumor cells (chemotherapy). Light was shown to disrupt the grenade-like structure of NPs to release AF-DOX NCs as well as DOX from NCs in low-pH intercellular environments. In vitro and in vivo studies showed that the structure of AF-DOX NCs was disassembled to release DOX, which then killed the cancer cells in organelles with acidic environments. In vivo studies showed that the ADNIR NP-decorated with NIR dye facilitated tracking of the accumulated NPs at the tumor site using an IVIS imaging system. Overall, targeted ADNIR NPs with dual-release mechanisms were developed for use in photothermal theranostic and chemotherapy. This modality has high potential for application in cancer treatment and clinical translation for drug delivery and imaging.

Revival of collective water structure and dynamics in reverse micelles brought about by protein encapsulation

A novel mechanism of depolarization in reverse micelles with zwitterionic surfactants and containing polar species but lacking ions is reported.

Protein charge transfer absorption spectra: an intrinsic probe to monitor structural and oligomeric transitions in proteins

The utility of ProCharTS as an intrinsic spectral probe to track protein aggregation and monitor conformational changes is reported.

Macromolecular crowding and the importance of proper hydration for the structure and dynamics of protein solutions

Extensive computational studies of ubiquitin crowding with a special focus on protein hydration directly visible in dielectric spectra.