Interaction of caffeine and sulfadiazine with lysozyme adsorbed at colloidal metal nanoparticle interface: influence on drug transport ability and antibacterial activity

The modulated bioactivity of proteins immobilized on nanoparticle (NP) interfaces is of tremendous interest toward designing better therapeutic and diagnostic tools. In this work, binding behavior and the antibacterial activity of free lysozyme (LYS) as well as its non-covalent assembly with silver (Ag) and gold (Au) colloidal NPs were compared in presence of two model drugs, viz. sulfadiazine (SDZ) and caffeine (CAF). Intrinsic protein fluorescence was found to quench due to the formation drug–protein complex in case of CAF resulting a linear Stern–Volmer (SV) plot with K_SV = 1.83 × 10³ M^?1.On the other hand, a positive deviation beyond [SDZ] ~0.15 mM is explained due to the formation of a fluorophore – quencher sphere with radius of 13.85 ± 1.80 Å that results almost one order of magnitude higher K_SV (1.75 × 10⁴ M^?1). Molecular docking calculation also predicts relatively more stabilized complex of SDZ with LYS in comparison to CAF (ΔE ~ 3 kJ mol^?1). Synchronous fluorescence results corresponding to Trp and Tyr residues as well as FTIR spectra in the amide I region of LYS confirms minimal deformation in the LYS secondary structure on adsorption to spherical NP surface. Although the nature of LYS–drug interaction remains invariant, the extent of quenching interaction as well as the drug binding ability is strongly modulated in presence of NPs. Further, the antibacterial activity of LYS in presence of the investigated drugs shows 9–14% upsurge with AuNP, in sharp contrast to ca. 31–34% decrease in AgNP.     

Environmental filtering predicts plant‐community trait distribution and diversity: Kettle holes as models of meta‐community systems

• Meta‐communities of habitat islands may be essential to maintain biodiversity in anthropogenic landscapes allowing rescue effects in local habitat patches. To understand the species‐assembly mechanisms and dynamics of such ecosystems, it is important to test how local plant‐community diversity and composition is affected by spatial isolation and hence by dispersal limitation and local environmental conditions acting as filters for local species sorting.We used a system of 46 small wetlands (kettle holes)—natural small‐scale freshwater habitats rarely considered in nature conservation policies—embedded in an intensively managed agricultural matrix in northern Germany. We compared two types of kettle holes with distinct topographies (flat‐sloped, ephemeral, frequently plowed kettle holes vs. steep‐sloped, more permanent ones) and determined 254 vascular plant species within these ecosystems, as well as plant functional traits and nearest neighbor distances to other kettle holes.Differences in alpha and beta diversity between steep permanent compared with ephemeral flat kettle holes were mainly explained by species sorting and niche processes and mass effect processes in ephemeral flat kettle holes. The plant‐community composition as well as the community trait distribution in terms of life span, breeding system, dispersal ability, and longevity of seed banks significantly differed between the two habitat types. Flat ephemeral kettle holes held a higher percentage of non‐perennial plants with a more persistent seed bank, less obligate outbreeders and more species with seed dispersal abilities via animal vectors compared with steep‐sloped, more permanent kettle holes that had a higher percentage of wind‐dispersed species. In the flat kettle holes, plant‐species richness was negatively correlated with the degree of isolation, whereas no such pattern was found for the permanent kettle holes.Synthesis: Environment acts as filter shaping plant diversity (alpha and beta) and plant‐community trait distribution between steep permanent compared with ephemeral flat kettle holes supporting species sorting and niche mechanisms as expected, but we identified a mass effect in ephemeral kettle holes only. Flat ephemeral kettle holes can be regarded as meta‐ecosystems that strongly depend on seed dispersal and recruitment from a seed bank, whereas neighboring permanent kettle holes have a more stable local species diversity.

     

Redox signalling from NADPH oxidase targets metabolic enzymes and developmental proteins in Fusarium graminearum

NADPH oxidase (NOX) is one of the sources of reactive oxygen species (ROS) that modulates the activity of proteins through modifications of their cysteine residues. In a previous study, we demonstrated the importance of NOX in both the development and pathogenicity of the phytopathogen Fusarium graminearum. In this article, comparative proteomics between the wild-type and a Nox mutant of F. graminearum was used to identify active cysteine residues on candidate redox-sensing proteins. A two-dimensional gel approach based on labelling with monobromobimane (mBBR) identified 19 candidate proteins, and was complemented with a gel-free shotgun approach based on a biotin switch method, which yielded 99 candidates. The results indicated that, in addition to temporal regulation, a large number of primary metabolic enzymes are potentially targeted by NoxAB-generated ROS. Targeted disruption of these metabolic genes showed that, although some are dispensable, others are essential. In addition to metabolic enzymes, developmental proteins, such as the Woronin body major protein (FGSG_08737) and a glycosylphosphatidylinositol (GPI)-anchored protein (FGSG_10089), were also identified. Deletion of either of these genes reduced the virulence of F. graminearum. Furthermore, changing the redox-modified cysteine (Cys³²⁵) residue in FGSG_10089 to either serine or phenylalanine resulted in a similar phenotype to the FGSG_10089 knockout strain, which displayed reduced virulence and altered cell wall morphology; this underscores the importance of Cys³²⁵ to the function of the protein. Our results indicate that NOX-generated ROS act as intracellular signals in F. graminearum and modulate the activity of proteins affecting development and virulence in planta.     

Ligands for FKBP12 Increase Ca2+ Influx and Protein Synthesis to Improve Skeletal Muscle Function

Rapamycin at high doses (2–10 mg/kg body weight) inhibits mammalian target of rapamycin complex 1 (mTORC1) and protein synthesis in mice. In contrast, low doses of rapamycin (10 μg/kg) increase mTORC1 activity and protein synthesis in skeletal muscle. Similar changes are found with SLF (synthetic ligand for FKBP12, which does not inhibit mTORC1) and in mice with a skeletal muscle-specific FKBP12 deficiency. These interventions also increase Ca²⁺ influx to enhance refilling of sarcoplasmic reticulum Ca²⁺ stores, slow muscle fatigue, and increase running endurance without negatively impacting cardiac function. FKBP12 deficiency or longer treatments with low dose rapamycin or SLF increase the percentage of type I fibers, further adding to fatigue resistance. We demonstrate that FKBP12 and its ligands impact multiple aspects of muscle function.