Light-Fueled Rapid Macroscopic Motion by a Green Fluorescent Organic Crystal

CrystEngComm ◽  
2021 ◽  
Author(s):  
Prasenjit Giri ◽  
Abhrojyoti Mazumder ◽  
Dibyendu Dey ◽  
Souvik Garani ◽  
Anju Raveendran ◽  
...  
Keyword(s):  
Uv Light ◽  
Organic Crystal ◽  
Macroscopic Motion ◽  
Green Fluorescent ◽  
Macroscopic Response

We report here a new green fluorescent organic crystal of amide functionalized acrylonitrile derivative (E-ArF2) that displays various types of macroscopic response when illuminated with UV light (390 nm). The...

scholarly journals Rotavirus Virus-Like Particles as Surrogates in Environmental Persistence and Inactivation Studies

2004 ◽  
Vol 70 (7) ◽  
pp. 3904-3909 ◽  
Author(s):  
Santiago Caballero ◽  
F. Xavier Abad ◽  
Fabienne Loisy ◽  
Françoise S. Le Guyader ◽  
Jean Cohen ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Uv Light ◽  
Expression System ◽  
Baculovirus Expression System ◽  
Virus Removal ◽  
Virus Like Particles ◽  
Reverse Transcription Pcr ◽  
Actual Field ◽  
Uv Dose ◽  
Green Fluorescent

ABSTRACT Virus-like particles (VLPs) with the full-length VP2 and VP6 rotavirus capsid proteins, produced in the baculovirus expression system, have been evaluated as surrogates of human rotavirus in different environmental scenarios. Green fluorescent protein-labeled VLPs (GFP-VLPs) and particles enclosing a heterologous RNA (pseudoviruses), whose stability may be monitored by flow cytometry and antigen capture reverse transcription-PCR, respectively, were used. After 1 month in seawater at 20°C, no significant differences were observed between the behaviors of GFP-VLPs and of infectious rotavirus, whereas pseudovirus particles showed a higher decay rate. In the presence of 1 mg of free chlorine (FC)/liter both tracers persisted longer in freshwater at 20°C than infectious viruses, whereas in the presence of 0.2 mg of FC/liter no differences were observed between tracers and infectious rotavirus at short contact times. However, from 30 min of contact with FC onward, the decay of infectious rotavirus was higher than that of recombinant particles. The predicted Ct value for a 90% reduction of GFP-VLPs or pseudoviruses induces a 99.99% inactivation of infectious rotavirus. Both tracers were more resistant to UV light irradiation than infectious rotavirus in fresh and marine water. The effect of UV exposure was more pronounced on pseudovirus than in GFP-VLPs. In all types of water, the UV dose to induce a 90% reduction of pseudovirus ensures a 99.99% inactivation of infectious rotavirus. Recombinant virus surrogates open new possibilities for the systematic validation of virus removal practices in actual field situations where pathogenic agents cannot be introduced.

scholarly journals New Additive for Culture Media for Rapid Identification of Aflatoxin-ProducingAspergillus Strains

2001 ◽  
Vol 67 (10) ◽  
pp. 4858-4862 ◽  
Author(s):  
C. A. Fente ◽  
J. Jaimez Ordaz ◽  
B. I. Vázquez ◽  
C. M. Franco ◽  
A. Cepeda
Keyword(s):  
Culture Media ◽  
Uv Light ◽  
Rapid Identification ◽  
Fungal Culture ◽  
Simple Method ◽  
Long Wavelength ◽  
Cyclodextrin Derivative ◽  
Natural Fluorescence ◽  
Green Fluorescent ◽  
Bright Blue

ABSTRACT A new reliable, fast, and simple method for the detection of aflatoxigenic Aspergillus strains, consisting of the addition of a cyclodextrin (a methylated β-cyclodextrin derivative) to common media used for testing mycotoxin production ability, was developed. We propose the use of this compound as an additive for fungal culture media to enhance the natural fluorescence of aflatoxins. The production of aflatoxins coincided with the presence of a bright blue or blue-green fluorescent area surrounding colonies when observed under long-wavelength (365-nm) UV light after 3 days of incubation at 28°C. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by high-pressure liquid chromatography with fluorescence detection.

scholarly journals 1.8 Å bright-state structure of the reversibly switchable fluorescent protein Dronpa guides the generation of fast switching variants

2007 ◽  
Vol 402 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Andre C. Stiel ◽  
Simon Trowitzsch ◽  
Gert Weber ◽  
Martin Andresen ◽  
Christian Eggeling ◽  
...  
Keyword(s):  
Blue Light ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Uv Light ◽  
Structural Features ◽  
Trans Isomerization ◽  
Fluorescent State ◽  
Green Fluorescent ◽  
New Applications ◽  
Key Events

RSFPs (reversibly switchable fluorescent proteins) may be repeatedly converted between a fluorescent and a non-fluorescent state by irradiation and have attracted widespread interest for many new applications. The RSFP Dronpa may be switched with blue light from a fluorescent state into a non-fluorescent state, and back again with UV light. To obtain insight into the underlying molecular mechanism of this switching, we have determined the crystal structure of the fluorescent equilibrium state of Dronpa. Its bicyclic chromophore is formed spontaneously from the Cys62–Tyr63–Gly64 tripeptide. In the fluorescent state, it adopts a slightly non-coplanar cis conformation within the interior of a typical GFP (green fluorescent protein) β-can fold. Dronpa shares some structural features with asFP595, another RSFP whose chromophore has previously been demonstrated to undergo a cis–trans isomerization upon photoswitching. Based on the structural comparison with asFP595, we have generated new Dronpa variants with an up to more than 1000-fold accelerated switching behaviour. The mutations which were introduced at position Val157 or Met159 apparently reduce the steric hindrance for a cis–trans isomerization of the chromophore, thus lowering the energy barrier for the blue light-driven on-to-off transition. The findings reported in the present study support the view that a cis–trans isomerization is one of the key events common to the switching mechanism in RSFPs.

scholarly journals Labeling of peroxisomes with green fluorescent protein in living P. pastoris cells.

1996 ◽  
Vol 44 (6) ◽  
pp. 581-589 ◽  
Author(s):  
E Z Monosov ◽  
T J Wenzel ◽  
G H Lüers ◽  
J A Heyman ◽  
S Subramani
Keyword(s):  
Green Fluorescent Protein ◽  
Fusion Protein ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Alcohol Oxidase ◽  
Methylotrophic Yeast ◽  
Ultrastructural Localization ◽  
Yeast Cells ◽  
Fluorescent Properties ◽  
Green Fluorescent

We exploited the light-activated fluorescent properties of the green fluorescent protein (GFP) of the jellyfish Aequorea victoria for studies on the peroxisomal sorting of polypeptides. GFP and GFP-SKL (containing a C-terminal, tripeptide peroxisomal targeting signal, SKL) were expressed from a methanol-inducible, alcohol oxidase (AOX1) promoter in the methylotrophic yeast Pichia pastoris. GFP was cytosolic, whereas the GFP-SKL fusion protein was targeted to peroxisomes, as demonstrated by biochemical fractionation of organelles on Nycodenz gradients. Neither GFP nor GFP-SKL affected the viability of yeast cells but both were fluorescent on excitation with 395-nm UV light. The subcellular locations of GFP and GFP-SKL in living yeast cells were monitored by fluorescence microscopy and their fluorescence was coupled to photo-oxidation of diaminobenzidine (DAB), resulting in the deposition of electron-dense oxidized DAB at intracellular locations of GFP derivatives. This photooxidation procedure permitted facile ultrastructural localization of GFP in cells by electron microscopy, and provided further evidence that GFP produced in P. pastoris is cytosolic, whereas GFP-SKL is peroxisomal. The GFP-SKL fusion protein is therefore a versatile reporter for the peroxisomal compartment, with many applications for studies involving peroxisomal import and biogenesis.

scholarly journals Effects of Green Fluorescent Protein or β-Glucuronidase Tagging on the Accumulation and Pathogenicity of a Resistance-Breaking Lettuce mosaic virus Isolate in Susceptible and Resistant Lettuce Cultivars

2000 ◽  
Vol 13 (3) ◽  
pp. 316-324 ◽  
Author(s):  
Sylvie German-Retana ◽  
Thierry Candresse ◽  
Emmanuel Alias ◽  
René-Pierre Delbos ◽  
Olivier Le Gall
Keyword(s):  
Green Fluorescent Protein ◽  
Mosaic Virus ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Wild Type Virus ◽  
Lettuce Mosaic Virus ◽  
Recombinant Viruses ◽  
Virus Accumulation ◽  
Resistance Breaking ◽  
Green Fluorescent

The RNA genome of a resistance-breaking isolate of Lettuce mosaic virus (LMV-E) was engineered to express the jellyfish green fluorescent protein (GFP) or β-glucuronidase (GUS) fused to the helper-component proteinase (HC-Pro) to study LMV invasion and spread in susceptible and resistant lettuce cultivars. Virus accumulation and movement were monitored by either histochemical GUS assays or detection of GFP fluorescence under UV light. The GFP- and GUS-tagged viruses spread systemically in the susceptible lettuce cultivars Trocadero and Vanguard, where they induced attenuated symptoms, compared with the wild-type virus. Accumulation of the GFP-tagged virus was reduced but less affected than in the case of the GUS-tagged virus. Systemic movement of both recombinant viruses was very severely affected in Vanguard 75, a lettuce cultivar nearly isogenic to Vanguard but carrying the resistance gene mo12 . Accumulation of the recombinant viruses in systemically infected leaves was either undetectable (GUS-tag) or erratic, strongly delayed, and inhibited by as much as 90% (GFP-tag). As a consequence, and contrary to the parental virus, the recombinant viruses were not able to overcome the protection afforded by the mo12 gene. Taken together, these results indicate that GUS or GFP tagging of the HC-Pro of LMV has significant negative effects on the biology of the virus, abolishing its resistance-breaking properties and reducing its pathogenicity in susceptible cultivars.

scholarly journals Potyvirus-induced gene silencing: the dynamic process of systemic silencing and silencing suppression

2007 ◽  
Vol 88 (8) ◽  
pp. 2337-2346 ◽  
Author(s):  
Elin Gammelgård ◽  
Maradumane Mohan ◽  
Jari P. T. Valkonen
Keyword(s):  
Gene Silencing ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Deletion Mutants ◽  
Virus Induced Gene Silencing ◽  
Potato Virus A ◽  
Silencing Suppression ◽  
Dark Green ◽  
Green Fluorescent ◽  
Interfering Rna

Potato virus A (PVA; genus Potyvirus) was used for virus-induced gene silencing in a model system that included transgenic Nicotiana benthamiana (line 16c) expressing the gfp transgene for green fluorescent protein (GFP) and chimeric PVA (PVA–GFP) carrying gfp in the P1-encoding region. Infection of the 16c plants with PVA–GFP in five experiments resulted in a reproducible pattern of systemic gfp transgene silencing, despite the presence of the strong silencing-suppressor protein, HC-Pro, produced by the virus. PVA–GFP was also targeted by silencing, and virus-specific short interfering RNA accumulated from the length of the viral genome. Viral deletion mutants lacking the gfp insert appeared in systemically infected leaves and reversed silencing of the gfp transgene in limited areas. However, systemic gfp silencing continued in newly emerging leaves in the absence of the gfp-carrying virus, which implicated a systemic silencing signal that moved from lower leaves without interference by HC-Pro. Use of GFP as a visual marker revealed a novel, mosaic-like recovery phenotype in the top leaves. The leaf areas appearing red or purple under UV light (no GFP expression) contained little PVA and gfp mRNA, and corresponded to the dark-green islands observed under visible light. The surrounding green fluorescent tissues contained actively replicating viral deletion mutants that suppressed GFP silencing. Taken together, systemic progression of gene silencing and antiviral defence (RNA silencing) and circumvention of the silencing by the virus could be visualized and analysed in a novel manner.

Development of Green Fluorescent Protein–Expressing Bacterial Strains and Evaluation for Potential Use as Positive Controls in Sample Analyses

2005 ◽  
Vol 68 (4) ◽  
pp. 680-686 ◽  
Author(s):  
CHARLES W. NOAH ◽  
CHRISTINE I. SHAW ◽  
JACK S. IKEDA ◽  
KAREN S. KREUZER ◽  
JOHN N. SOFOS
Keyword(s):  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Positive Control ◽  
Diagnostic Methods ◽  
Feta Cheese ◽  
Green Fluorescent ◽  
Raw Shrimp ◽  
Potential Use ◽  
Positive Controls

Strains of enterohemorrhagic Escherichia coli O157:H7 and Salmonella Typhimurium were engineered to express the gene for a modified green fluorescent protein (GFP) and were evaluated for potential use as positive controls in sample analyses. The strains fluoresced when observed as colonies with a handheld UV lamp or as individual cells under a fluorescent microscope. The strains maintained their fluorescence following growth in three series of transfer experiments including 8 to 11 passages from broth to broth and twice for 15 consecutive transfers from broth onto Trypticase soy agar plates. Cultures also maintained stability in the ability to fluoresce when agar plates were refrigerated (4°C) for up to 12 days. Growth characteristics of the GFP-positive strains were comparable to those of corresponding control strains. The GFP-positive strains were successfully identified using rapid diagnostic methods and were differentiated from their corresponding non-GFP strains by pulsed-field gel electrophoresis but not by repetitive extragenic palindromic PCR. The GFP-positive and the control strains were recovered successfully from individually inoculated food samples (Feta cheese, raw shrimp, cooked shrimp, and cooked crawfish). However, in one Feta cheese sample and one raw shrimp sample inoculated with combined GFP-positive and GFP-negative cultures, colonies of the GFP-positive strains were not observed under UV light; fluorescing cells in one of the inoculated samples (raw shrimp) were revealed by microscopy. In general, the isolates from the inoculated foods were GFP positive by microscopic examination; the pure isolates could also be restreaked onto Trypticase soy agar, and colonies could be visually examined under UV light. Because GFP strains are not known to occur naturally in the environment, the use of the Salmonella GFP-positive strain may offer advantages as a positive control even when distinct and rare serotypes are available. The GFP-positive E. coli O157:H7 strain may also prove beneficial for use as a positive control strain for sample analyses.

scholarly journals Effect of Starvation and the Viable-but-Nonculturable State on Green Fluorescent Protein (GFP) Fluorescence in GFP-TaggedPseudomonas fluorescens A506

2000 ◽  
Vol 66 (8) ◽  
pp. 3160-3165 ◽  
Author(s):  
M. Lowder ◽  
A. Unge ◽  
N. Maraha ◽  
J. K. Jansson ◽  
J. Swiggett ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Uv Light ◽  
Membrane Integrity ◽  
Live Cells ◽  
Reporter System ◽  
Viable But Nonculturable ◽  
Nonculturable State ◽  
Green Fluorescent

ABSTRACT The green fluorescent protein (GFP) gene, gfp, of the jellyfish Aequorea victoria is being used as a reporter system for gene expression and as a marker for tracking prokaryotes and eukaryotes. Cells that have been genetically altered with thegfp gene produce a protein that fluoresces when it is excited by UV light. This unique phenotype allowsgfp-tagged cells to be specifically monitored by nondestructive means. In this study we determined whether agfp-tagged strain of Pseudomonas fluorescenscontinued to fluoresce under conditions under which the cells were starved, viable but nonculturable (VBNC), or dead. Epifluorescent microscopy, flow cytometry, and spectrofluorometry were used to measure fluorescence intensity in starved, VBNC, and dead or dying cells. Results obtained by using flow cytometry indicated that microcosms containing VBNC cells, which were obtained by incubation under stress conditions (starvation at 37.5°C), fluoresced at an intensity that was at least 80% of the intensity of nonstressed cultures. Similarly, microcosms containing starved cells incubated at 5 and 30°C had fluorescence intensities that were 90 to 110% of the intensity of nonstressed cells. VBNC cells remained fluorescent during the entire 6-month incubation period. In addition, cells starved at 5 or 30°C remained fluorescent for at least 11 months. Treatment of the cells with UV light or incubation at 39 or 50°C resulted in a loss of GFP from the cells. There was a strong correlation between cell death and leakage of GFP from the cells, although the extent of leakage varied depending on the treatment. Most dead cells were not GFP fluorescent, but a small proportion of the dead cells retained some GFP at a lower concentration than the concentration in live cells. Our results suggest that gfp-tagged cells remain fluorescent following starvation and entry into the VBNC state but that fluorescence is lost when the cells die, presumably because membrane integrity is lost.

Electron microscopy of keratinocytes cultured on a collagen substrate used as an allograft for the treatment of chronic wounds

1992 ◽  
Vol 50 (2) ◽  
pp. 1104-1105
Author(s):  
Debby A. Jennings ◽  
Michael J. Morykwas ◽  
Louis C. Argenta
Keyword(s):  
Electron Microscopy ◽  
Cell Suspension ◽  
Single Cell ◽  
Chronic Wounds ◽  
Mechanical Stability ◽  
Uv Light ◽  
Type I ◽  
Single Cell Suspension ◽  
Collagen Substrate ◽  
Dermal Collagen

Grafts of cultured allogenic or autogenic keratlnocytes have proven to be an effective treatment of chronic wounds and burns. This study utilized a collagen substrate for keratinocyte and fibroblast attachment. The substrate provided mechanical stability and augmented graft manipulation onto the wound bed. Graft integrity was confirmed by light and transmission electron microscopy.Bovine Type I dermal collagen sheets (100 μm thick) were crosslinked with 254 nm UV light (13.5 Joules/cm2) to improve mechanical properties and reduce degradation. A single cell suspension of third passage neonatal foreskin fibroblasts were plated onto the collagen. Five days later, a single cell suspension of first passage neonatal foreskin keratinocytes were plated on the opposite side of the collagen. The grafts were cultured for one month.The grafts were fixed in phosphate buffered 4% formaldehyde/1% glutaraldehyde for 24 hours. Graft pieces were then washed in 0.13 M phosphate buffer, post-fixed in 1% osmium tetroxide, dehydrated, and embedded in Polybed 812.

A photoelectron microscope study of surfaces

1989 ◽  
Vol 47 ◽  
pp. 10-11
Author(s):  
W. Engel ◽  
M. Kordesch ◽  
A. M. Bradshaw ◽  
E. Zeitler
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Field Strength ◽  
Uv Light ◽  
Physical Property ◽  
Photon Flux ◽  
Mercury Lamp ◽  
Object Surface ◽  
The Sixties ◽  
Physical Features

Photoelectron microscopy is as old as electron microscopy itself. Electrons liberated from the object surface by photons are utilized to form an image that is a map of the object's emissivity. This physical property is a function of many parameters, some depending on the physical features of the objects and others on the conditions of the instrument rendering the image.The electron-optical situation is tricky, since the lateral resolution increases with the electric field strength at the object's surface. This, in turn, leads to small distances between the electrodes, restricting the photon flux that should be high for the sake of resolution.The electron-optical development came to fruition in the sixties. Figure 1a shows a typical photoelectron image of a polycrystalline tantalum sample irradiated by the UV light of a high-pressure mercury lamp.

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