Search results for "fluorescence"

Dual emission of a bis(pyrene)-functionalized, perbenzylated beta-cyclodextrin

2008

A bis(pyrene)-functionalized β-cyclodextrin (1) has been prepared in two steps from perbenzylated β-cyclodextrin. This compound shows dual emission properties, which arise from the pyrenyl chromophores. Upon excitation of 1 at 355 nm, monomer blue fluorescence (386, 407 and 428 nm) is observed in DMSO solution, whereas excimer green fluorescence (477 nm) is seen upon addition of ≥20 vol% water in DMSO. This suggests that modified β-cyclodextrin 1 changes its shape in response to the environment. The sensing properties of 1 towards carboxylic acids and alcohols were investigated in H2O–DMSO (80 : 20 v/v). Monomer fluorescence is restored selectively by medium length normal carboxylic acids, …

Preferential localization of Lactococcus lactis cells entrapped in a caseinate/alginate phase separated system.

2013

International audience; This study aimed to entrap bioprotective lactic acid bacteria in a sodium caseinate/sodium alginate aqueous two-phase system. Phase diagram at pH = 7 showed that sodium alginate and sodium caseinate were not miscible when their concentrations exceeded 1% (w/w) and 6% (w/w), respectively. The stability of the caseinate/alginate two-phase system was also checked at pH values of 6.0 and 5.5. Lactococcus lactis subsp. lactis LAB3 cells were added in a 4% (w/w) caseinate/1.5% (w/w) alginate two-phase system at pH = 7. Fluorescence microscopy allowed to observe that the caseinate-rich phase formed droplets dispersed in a continuous alginate-rich phase. The distribution of …

Rapid identification of minor histocompatibility antigen HA-1 subtypes H and R using fluorescence-labeled oligonucleotides

2000

Acknowledgments: We thank Brigitte Schuch and Karola Schmidt for excellent technical assistance. This work was supported by a grant of the Deutsche Krebshilfe (Nr. 70-2427 and Nr. 70-2428). Abstract: Donor-recipient disparitiy of the minor histocompatibility antigen HA-1 is relevant for the development of graft-versus-host disease after HLA-matched sibling allogeneic bone marrow transplantation in HLA-A*0201-positive individuals. Two different alleles of HA-1 with a single amino acid polymorphism have been identified. Here we describe a time- and cost-efficient method for HA-1 typing of genomic DNA, using site-specific hybridization probes with the LightCycler. This method was compared with…

Measurement and correction of atmospheric effects in O<inf>2</inf>-B and O<inf>2</inf>-A absorption bands in the context of s…

2014

Under sun-light illumination, the shape of the atmospheric oxygen bands (O 2 -B, 687 nm and O 2 -A, 760 nm) of the vegetation radiance is modified by chlorophyll fluorescence. However for far-range measurements, atmospheric effects also modify this shape. In this study, measurements in O 2 -A and O 2 -B absorption bands have been performed at different altitudes up to 3123 m over bare soil and wheat fields. It is observed that bands depth increase significantly with altitude. In O 2 -B band, the total magnitude of variation is of the same order of magnitude as the change induced by vegetation fluorescence, while it is much greater in O 2 -A band. We used MODTRAN 4 to correct measurements fr…

Aminoquinolines: Fluorescent sensors to DNA – A minor groove probe. Experimental and in silico studies

2023

An aminoquinoline (AQ4) was developed and proven to be a new and efficient DNA minor groove fluorescent probe. The specificity for DNA minor groove was attested by comparing it with well-established DNA probes such as Hoechst stain, acridine orange, and ethidium bromide. AQ4 was similar to the Hoechst stain, a classic minor groove probe, and opposite to acridine orange and ethidium bromide, the typical intercalating probes. An advantage of AQ4 to the Hoechst stain was the higher fluorescent signal-to-noise ratio (+DNA/-DNA). The interaction with DNA leads to an exclusive fluorescent band centered at 590 nm. The red-shifted fluorescent band is associated with a new absorption band (490 nm), …

Concentration dependence of amplified spontaneous emission in two oligo-(p-phenylenevinylene) derivatives

2005

Amplified spontaneous emission sASEd in optically pumped polystyrene sPSd films doped with two different oligo-sp-phenylenevinylened derivatives sOPVsd, with three s3-OPVd and five s5-OPVd monomer units is reported. It is observed that there is a maximum content of oligomer s25 wt. % for 3-OPV and 20 wt. % for 5-OPVd that can be introduced in the films, due to degradation sin 3-OPVd and ASE quenching sin 5-OPVd. Optimal concentrations swith minimum pump-intensity thresholds for the observation of ASEd of 15 wt. % and 9 wt. % are measured for the trimer and the pentamer, respectively. The concentration dependence of the ASE threshold is discussed in terms of the optical absorption spectra. G…

Amyloid Fibrils Formation of Concanavalin A at Basic pH

2011

Mechanisms of partial unfolding and aggregation of proteins are of extreme interest in view of the fact that several human pathologies are characterized by the formation and deposition of protein-insoluble material, mainly composed of amyloid fibrils. Here we report on an experimental study on the heat-induced aggregation mechanisms, at basic pH, of concanavalin A (ConA), used as a model system. Thioflavin T (ThT) fluorescence and multiangle light scattering allowed us to detect different intertwined steps in the formation of ConA aggregates. In particular, the ThT fluorescence increase, observed in the first phase of aggregation, reveals the formation of intermolecular β-sheet structure wh…

Concanavalin A fibrils formation from Coagulation of Long-lived" Crinkled" Intermediates

2013

Kinetics of different processes in human insulin amyloid formation.

2007

Human insulin has long been known to form amyloid fibrils under given conditions. The molecular basis of insulin aggregation is relevant for modeling the amyloidogenesis process, which is involved in many pathologies, as well as for improving delivery systems, used for diabetes treatments. Insulin aggregation displays a wide variety of morphologies, from small oligomeric filaments to huge floccules, and therefore different specific processes are likely to be intertwined in the overall aggregation. In the present work, we studied the aggregation kinetics of human insulin at low pH and different temperatures and concentrations. The structure and the morphogenesis of aggregates on a wide range…

(E)-2-Cyano-3-(5′-piperidin-1-yl-2,2′-bithien-5-yl)acrylic Acid: A Fluorescent Probe for Detecting Prefibrillar Oligomers

2013

The synthesis of (E)-2-cyano-3-(5′-piperidin-1-yl-2,2′-bithien-5-yl)acrylic acid, a novel amyloid aggregation fluorescent probe, is reported. This new probe is able to monitor soluble oligomeric aggregates after 24 h, at which time Thioflavin T emission, commonly used to monitor amyloid fibril formation, remains unchanged. Atomic force microscopy, native polyacrylamide gel electrophoresis, and dynamic light scattering confirm that the earlier stages of aggregation are prefibrillar oligomeric species not possessing the amyloid structure. This new molecular scaffold expands the toolbox of fluorescent probes for the identification of prefibrillar oligomers, which is needed in studies aimed at …