Biologically synthesized green silver nanoparticles from leaf extract of Vitex negundo L. induce growth-inhibitory effect on human colon cancer cell line HCT15

Nanomedicine concerns the use of precision-engineered nanomaterials to develop novel therapeutic and diagnostic modalities for human use. The present study demonstrates the efficacy of silver nanoparticles (AgNPs) biosynthesis from leaf extract of Vitex negundo L. as an antitumor agent using human colon cancer cell line HCT15. The AgNPs synthesis was determined by UV–visible spectrum and it was further characterized by field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR) analysis. The toxicity was evaluated using changes in cell morphology, cell viability, nuclear fragmentation, cell cycle and comet assay. The percentage of cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Our results showed that biosynthesized silver nanoparticles inhibited proliferation of human colon cancer cell line HCT15 with an IC₅₀ of 20 μg/ml at 48 h incubation. AgNPs were shown to promote apoptosis as seen in the nuclear morphological examination study using propidium iodide staining and DNA fragmentation by single cell gel electrophoresis technique. Biosynthesized AgNPs arrested HCT15 cells at G₀/G₁ and G₂/M phases with corresponding decrease in S-phase. These results suggest that AgNPs may exert its antiproliferative effects on colon cancer cell line by suppressing its growth, arresting the G₀/G₁-phase, reducing DNA synthesis and inducing apoptosis.     

Iron uptake and transport by the carboxymycobactin-mycobactin siderophore machinery of Mycobacterium tuberculosis is dependent on the iron-regulated protein HupB

BioMetals - Iron-starved Mycobacterium tuberculosis utilises the carboxymycobactin-mycobactin siderophore machinery to acquire iron. These two siderophores have high affinity for ferric iron and...     

Anionic Antimicrobial and Anticancer Peptides from Plants

Anionic antimicrobial peptides (AAMPs) have been identified in a wide variety of plant species with net charges that range between ?1 and ?7 and structures that include: extended conformations, α-helical architecture and cysteine stabilized scaffolds. These peptides commonly exist as multiple isoforms within a given plant and have a range of biological activities including the ability to kill cancer cells as well as phytopathogenic bacteria, fungi, pests, molluscs, and other predatory species. In general, the killing mechanisms underpinning these activities are poorly understood although they appear to involve attack on intracellular targets such as DNA along with compromise of cell envelope integrity through lysis of the cell wall via chitin-binding and/or permeabilisation of the plasma membrane via lipid interaction. It is now becoming clear that AAMPs participate in the innate immune response of plants and make a major contribution to the arsenal of defence toxins produced by these organisms to compensate for their lack of some defence mechanisms possessed by mammals, such as mobility and a somatic adaptive immune system. Based on their biological properties, a number of potential uses for plant AAMPs have been suggested, including therapeutically useful anticancer agents and novel antimicrobial compounds, which could be utilized in a variety of scenarios, ranging from the protection of crops to the disinfection of hospital environments.     

Biosynthetic substitution of tyrosine in green fluorescent protein with its surrogate fluorotyrosine in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Introduction of a fluorine moiety into green fluorescent protein offers an interesting novel spectral variant. The calculated binding energy of fluorotyrosine (F-Tyr) (−8.42 kcal/mol) for tyrosyl tRNA synthetase was moderately higher than that of tyrosine (Tyr) (−8.36 kcal/mol). This result directly correlated with the expression level of F-Tyr containing GFP (38 mg/l), which was comparably higher than that of the parent GFP expression level (34 mg/l). Finally, we generated a model structure for GFP to assess possible interaction in the chromophore of the protein structure, which plays an important role in determining the spectral and folding behaviors of the F-Tyr incorporated GFP variant.     

Detection of ricin using a carbon nanofiber based biosensor

We report ricin detection using antibody and aptamer probes immobilized on a nanoelectrode array (NEA) consisting of vertically aligned carbon nanofibers (VACNFs). These biosensor chips are fabricated on a wafer scale using steps common in integrated circuit manufacturing. Electrochemical impedance spectroscopy is used to characterize the detection event and the results indicate that the electron transfer resistance changes significantly after the ricin protein binds to the probe. Further confirmation is obtained from evaluation of the electrode surface by atomic force microscopy which clearly shows a change in height from the bare electrode to the surface bound by the probe-protein.     

Two new complete genome sequences offer insight into host and tissue specificity of plant pathogenic Xanthomonas spp

Xanthomonas is a large genus of bacteria that collectively cause disease on more than 300 plant species. The broad host range of the genus contrasts with stringent host and tissue specificity for individual species and pathovars. Whole-genome sequences of Xanthomonas campestris pv. raphani strain 756C and X. oryzae pv. oryzicola strain BLS256, pathogens that infect the mesophyll tissue of the leading models for plant biology, Arabidopsis thaliana and rice, respectively, were determined and provided insight into the genetic determinants of host and tissue specificity. Comparisons were made with genomes of closely related strains that infect the vascular tissue of the same hosts and across a larger collection of complete Xanthomonas genomes. The results suggest a model in which complex sets of adaptations at the level of gene content account for host specificity and subtler adaptations at the level of amino acid or noncoding regulatory nucleotide sequence determine tissue specificity.     

Extra-Lysosomal Localization of Arylsulfatase B in Human Colonic Epithelium

The enzyme arylsulfatase B (N-acetylgalactosamine-4-sulfatase; ARSB; ASB) removes 4-sulfate groups from the sulfated glycosaminoglycans (sGAG) chondroitin-4-sulfate (C4S) and dermatan sulfate (DS). Inborn deficiency of ARSB leads to the lysosomal storage disease mucopolysaccharidosis VI, characterized by accumulation of sGAG in vital organs, disruption of normal physiological processes, severe morbidity, and premature death. Recent published work demonstrated extra-lysosomal localization with nuclear and cell membrane ARSB observed in bronchial and colonic epithelial cells, cerebrovascular cells, and hepatic cells. In this report, the authors present ARSB immunostaining in a colonic microarray and show differences in distribution, intensity, and pattern of ARSB staining among normal colon, adenomas, and adenocarcinomas. Distinctive, intense luminal membrane staining was present in the normal epithelial cells but reduced in the malignancies and less in the grade 3 than in the grade 1 adenocarcinomas. In the normal cores, a distinctive pattern of intense cytoplasmic positivity at the luminal surface was followed by reduced staining deeper in the crypts. ARSB enzymatic activity was significantly greater in normal than in malignant tissue. These study findings affirm extra-lysosomal localization of ARSB and suggest that altered ARSB immunostaining and reduced activity may be useful indicators of malignant transformation in human colonic tissue.     

Insights into metalloregulation by M-box riboswitch RNAs via structural analysis of manganese-bound complexes

The M-box riboswitch couples intracellular magnesium levels to expression of bacterial metal transport genes. Structural analyses on other riboswitch RNA classes, which typically respond to a small organic metabolite, have revealed that ligand recognition occurs through a combination of base-stacking, electrostatic, and hydrogen-bonding interactions. In contrast, the M-box RNA triggers a change in gene expression upon association with an undefined population of metals, rather than responding to only a single ligand. Prior biophysical experimentation suggested that divalent ions associate with the M-box RNA to promote a compacted tertiary conformation, resulting in sequestration of a short sequence tract otherwise required for downstream gene expression. Electrostatic shielding from loosely associated metals is undoubtedly an important influence during this metal-mediated compaction pathway. However, it is also likely that a subset of divalent ions specifically occupies cation binding sites and promotes proper positioning of functional groups for tertiary structure stabilization. To better elucidate the role of these metal binding sites, we resolved a manganese-chelated M-box RNA complex to 1.86 Å by X-ray crystallography. These data support the presence of at least eight well-ordered cation binding pockets, including several sites that had been predicted by biochemical studies but were not observed in prior structural analysis. Overall, these data support the presence of three metal-binding cores within the M-box RNA that facilitate a network of long-range interactions within the metal-bound, compacted conformation.     

Analysis of transgene(s) (psy+crtI) inheritance and its stability over generations in the genetic background of indica rice cultivar Swarna

Rice the major staple food crop which feeds more than half of the world’s population but, lacks pathway to synthesize and accumulate provitamin A in endosperm therefore rice eaters particularly children, and pregnant women suffer due to vitamin A deficiency. The pathway for provitamin A synthesis in rice endosperm has been engineered and transgenic rice lines have yellow endosperm, called ‘Golden Rice’. The present study aimed at studying the inheritance of transgene(s) in six transgenic events of ‘Golden Rice’ and transfer of provitamin A trait from transgenic lines to a widely grown mega rice variety Swarna. The events E1, R1 and W1 showed normal Mendelian inheritance in F₂, BC₁F₁ and BC₁F₂ generations. The event W1 was studied in BC₁F₃ as well and showed normal Mendelian inheritance of 3:1. The inheritance pattern in L1 event in BC₁F₁ and BC₁F₂ showed normal Mendelian inheritance following expected ratio 1:1 and 3:1 respectively. The two events G1 and T1 showed distorted segregation in BC₁F₂ and BC₂F₂ respectively in Swarna genetic background. In G1 event, transgene inheritance showed segregation distortion in BC₁F₂ in favour of transgene negative plants. In T1 event, inheritance followed expected Mendelian segregation in BC₁F₁, BC₂F₁ and BC₂F₂, generations. However, when tested against co-dominant inheritance 1:2:1 pattern in BC₂F₂, segregation distortion was observed with less than the expected transgene homozygotes. While against 3:1 ratio, it showed the expected segregation pattern in BC₂F₂ generation. Segregation distortion probably due to differential transmission of transgene positive/negative gametes through either/both parents which needs further study.