The Dimensionality of Hydrogen Bond Networks Induces Diverse Physical Properties of Peptide Crystals.

Short peptides are attractive building blocks for the fabrication of self-assembled materials with significant biological, chemical, and physical properties. The microscopic and macroscopic properties of assemblies are usually closely related to the dimensionality of formed hydrogen bond networks. Here, two completely different supramolecular architectures connected by distinct hydrogen bond networks were obtained by simply adding a hydroxyl group to switch from cyclo-tryptophan-alanine (cyclo-WA) to cyclo-tryptophan-serine (cyclo-WS). While hydroxyl-bearing cyclo-WS molecules provided an additional hydrogen bond donor that links to adjacent molecules, forming a rigid three-dimensional network, cyclo-WA arranged into a water-mediated zipper-like structure with a softer two-dimensional layer template. This subtle alteration resulted in a 14-fold enhancement of Young's modulus values in cyclo-WS compared to cyclo-WA. Both cyclo-dipeptides exhibit biocompatibility, high fluorescence, and piezoelectricity. The demonstrated role of dimensionality of hydrogen bond networks opens new avenues for rational design of materials with precise morphologies and customizable properties for bioelectronic applications.

Preventing biofilm formation and eradicating pathogenic bacteria by Zn doped histidine derived carbon quantum dots.

Bacterial infections are of major medical concern due to antibiotic resistance. Carbon quantum dots (CDs) have emerged as potentially excellent biomaterials for multifunctional applications due to their low toxicity, outstanding water solubility, high fluorescence, and high biocompatibility. All of these properties allow CDs to be exceptional biomaterials for inhibiting the growth of bacteria and stopping biofilm formation due to their strong binding affinity, cell wall penetration, and solubilizing biofilm in water. Here, we describe a strategy for one-pot synthesis of histidine-derived zinc-doped N-doped CDs (Zn-NCDs) by a hydrothermal method for inhibiting the growth of both Gram-positive and Gram-negative bacteria without harming mammalian cells. The NCDs and Zn-NCDs showed uniform sizes (∼6 nm), crystallinity, good photostability, high quantum yield (76%), and long decay time (∼5 ns). We also studied their utilization for live cell bio-imaging and the antimicrobial properties towards the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa. Importantly, the Zn-NCDs could penetrate the biofilm and bacterial cell wall to effectively inhibit the growth of bacteria and subsequently inhibit biofilm formation. Thus, the structure, chemical composition, and low toxicity properties of the newly-developed Zn-NCDs exemplify a promising novel method for the preparation of nano-level antibacterial drugs.

LY6S, a New IFN-Inducible Human Member of the Ly6a Subfamily Expressed by Spleen Cells and Associated with Inflammation and Viral Resistance.

Syntenic genomic loci on human chromosome 8 and mouse chromosome 15 (mChr15) code for LY6/Ly6 (lymphocyte Ag 6) family proteins. The 23 murine Ly6 family genes include eight genes that are flanked by the murine Ly6e and Ly6l genes and form an Ly6 subgroup referred to in this article as the Ly6a subfamily gene cluster. Ly6a, also known as Stem Cell Ag-1 and T cell-activating protein, is a member of the Ly6a subfamily gene cluster. No LY6 genes have been annotated within the syntenic LY6E to LY6L human locus. We report in this article on LY6S, a solitary human LY6 gene that is syntenic with the murine Ly6a subfamily gene cluster, and with which it shares a common ancestry. LY6S codes for the IFN-inducible GPI-linked LY6S-iso1 protein that contains only 9 of the 10 consensus LY6 cysteine residues and is most highly expressed in a nonclassical spleen cell population. Its expression leads to distinct shifts in patterns of gene expression, particularly of genes coding for inflammatory and immune response proteins, and LY6S-iso1-expressing cells show increased resistance to viral infection. Our findings reveal the presence of a previously unannotated human IFN-stimulated gene, LY6S, which has a 1:8 ortholog relationship with the genes of the Ly6a subfamily gene cluster, is most highly expressed in spleen cells of a nonclassical cell lineage, and whose expression induces viral resistance and is associated with an inflammatory phenotype and with the activation of genes that regulate immune responses.

E4orf4 induces PP2A- and Src-dependent cell death in Drosophila melanogaster and at the same time inhibits classic apoptosis pathways.

The adenovirus E4orf4 protein regulates the progression of viral infection, and when expressed alone in mammalian tissue culture cells it induces protein phosphatase 2A (PP2A)-B55- and Src-dependent cell death, which is more efficient in oncogene-transformed cells than in normal cells. This form of cell death is caspase-independent, although it interacts with classic caspase-dependent apoptosis. PP2A-B55-dependent E4orf4-induced toxicity is highly conserved in evolution from yeast to mammalian cells. In this work we investigated E4orf4-induced cell death in a whole multicellular organism, Drosophila melanogaster. We show that E4orf4 induced low levels of cell killing, caused by both caspase-dependent and -independent mechanisms. Drosophila PP2A-B55 (twins/abnormal anaphase resolution) and Src64B contributed additively to this form of cell death. Our results provide insight into E4orf4-induced cell death, demonstrating that in parallel to activating caspase-dependent apoptosis, E4orf4 also inhibited this form of cell death induced by the proapoptotic genes reaper, head involution defective, and grim. The combination of both induction and inhibition of caspase-dependent cell death resulted in low levels of tissue damage that may explain the inefficient cell killing induced by E4orf4 in normal cells in tissue culture. Furthermore, E4orf4 inhibited JNK-dependent cell killing as well. However, JNK inhibition did not impede E4orf4-induced toxicity and even enhanced it, indicating that E4orf4-induced cell killing is a distinctive form of cell death that differs from both JNK- and Rpr/Hid/Grim-induced forms of cell death.

Microtubules of guard cells are light sensitive.

Guard cells of stomata are characterized by ordered bundles of microtubules radiating from the ventral side toward the dorsal side of the cylindrical cell. It was suggested that microtubules play a role in directing the radial arrangement of the cellulose micro-fibrils of guard cells. However, the role of microtubules in daily cycles of opening and closing of stomata is not clear. The organization of microtubules in guard cells of Commelina communis leaves was studied by analysis of three-dimensional immunofluorescent images. It was found that while guard cell microtubules in the epidermis of leaves incubated in the light were organized in parallel, straight and dense bundles, in the dark they were less straight and oriented randomly near the stomatal pore. The effect of blue and red light on the organization of guard cell microtubules resembled the effects of white light and dark respectively. When stomata were induced to open in the dark with fusicoccin, microtubules remained in the dark configuration. Furthermore, when incubated in the light, guard cell microtubules were more resistant to oryzalin. Similarly, microtubules of Arabidopsis guard cells, expressing green fluorescent protein-tubulin alpha 6, were disorganized in the dark, but were organized in parallel arrays in the presence of white light. The dynamics of microtubule rearrangement upon transfer of intact leaves from dark to light was followed in single stomata, showing that an arrangement of microtubules typical for light conditions was obtained after 1 h in the light. Our data suggest that microtubule organization in guard cells is responsive to light signals.