Restricted intramolecular rotation of fluorescent molecular rotors at the periphery of aqueous microdroplets in oil

Abstract Fluorescent molecular rotor dyes, including Cy3, Cy5, and Alexa Fluor 555, dissolved in micron-sized aqueous droplets (microdroplets) in oil were excited, and the fluorescence intensity was recorded as function of time. We observed lengthening of the fluorescence lifetime of these dyes at the water–oil periphery, which extended several microns inward. This behavior shows that intramolecular rotation is restricted at and near the microdroplet interface. Lengthened lifetimes were observed in water microdroplets but not in microdroplets composed of organic solvents. This lifetime change was relatively insensitive to added glycerol up to 60%, suggesting that solution viscosity is not the dominant mechanism. These restricted intramolecular rotations at and near the microdroplet periphery are consistent with the reduced entropy observed in chemical reactions in microdroplets compared to the same reaction conditions in bulk solution and helps us further understand why microdroplet chemistry differs so markedly from bulk-phase chemistry.

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Gold nanoclusters and fluorescence-based sensing

10.32469/10355/65454 ◽

2017 ◽

Author(s):

◽

Xi Chen

Keyword(s):

Fluorescence Intensity ◽

Cholesterol Oxidase ◽

Gold Nanoclusters ◽

Green Emission ◽

Mapping Method ◽

Metal Nanoclusters ◽

Molecular Rotor ◽

Great Resistance ◽

University Of Missouri ◽

Thermal Reversibility

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The main topic of this dissertation focuses on development of analytical methods, mainly modification and application of metal nanoclusters in fluorescence-based sensing. Based on bovine serum albumin passivated gold nanoclusters (AuNCs@BSA) we firstly developed a fluorescent biosensor platform, combining cholesterol oxidase with assistance of surfactant, for selective detection of water insoluble analyte, cholesterol in aqueous condition. Moreover, we designed a series of modification strategy to enhence thermal reversibility of AuNCs@BSA, aiming at reducing hysteresis remained during thermal cycles. Taking advantage of optimized thermal reversibility in terms of fully recoverable fluorescence intensity, analytical performance of modified AuNCs@BSA was investigated and an aqueous-phase temperature sensor was achieved. In addition to AuNCs, we developed novel glutathione stabilized copper NCs with green-emission in assistance of ascorbic acid reduction, which showed great resistance to nitro compounds. Further, analytical application of as-prepared Cu NCs to ratiometric sensing on explosive molecules, cooperating with AuNCs@BSA, was investigated. In the last, a novel and facile temperature mapping method using ionic liquid and organic fluorescent molecular rotor were described. Making use of viscosity-sensitive fluorescent dye, temperature was converted to ratio value of fluorescence intensity and recorded, enabling visualized thermal map.

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Phase-Field Modeling of Freeze Concentration of Protein Solutions

Polymers ◽

10.3390/polym11010010 ◽

2018 ◽

Vol 11 (1) ◽

pp. 10 ◽

Cited By ~ 2

Author(s):

Tai-Hsi Fan ◽

Ji-Qin Li ◽

Bruna Minatovicz ◽

Elizabeth Soha ◽

Li Sun ◽

...

Keyword(s):

Phase Field ◽

Liquid Solution ◽

Solute Concentration ◽

Ice Crystals ◽

Mean Field Approximation ◽

Solution Viscosity ◽

Bulk Solution ◽

Freezing Process ◽

Freeze Concentration ◽

Solute Exclusion

Bulk solutions of therapeutic proteins are often frozen for long-term storage. During the freezing process, proteins in liquid solution redistribute and segregate in the interstitial space between ice crystals. This is due to solute exclusion from ice crystals, higher viscosity of the concentrated solution, and space confinement between crystals. Such segregation may have a negative impact on the native conformation of protein molecules. To better understand the mechanisms, we developed a phase-field model to describe the growth of ice crystals and the dynamics of freeze concentration at the mesoscale based on mean field approximation of solute concentration and the underlying heat, mass and momentum transport phenomena. The model focuses on evolution of the interfaces between liquid solution and ice crystals, and the degree of solute concentration due to partition, diffusive, and convective effects. The growth of crystals is driven by cooling of the bulk solution, but suppressed by a higher solute concentration due to increase of solution viscosity, decrease of freezing point, and the release of latent heat. The results demonstrate the interplay of solute exclusion, space confinement, heat transfer, coalescence of crystals, and the dynamic formation of narrow gaps between crystals and Plateau border areas along with correlations of thermophysical properties in the supercooled regime.

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Accelerated synthesis of energetic precursor cage compounds using confined volume systems

Scientific Reports ◽

10.1038/s41598-021-02945-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hilary M. Brown ◽

Karan R. Doppalapudi ◽

Patrick W. Fedick

Keyword(s):

Solution Phase ◽

Rapid Screening ◽

Bulk Solution ◽

Cage Structure ◽

Reaction Conditions ◽

Cage Compounds ◽

Cage Compound ◽

Reaction Acceleration ◽

Energetic Compound ◽

Reducing Costs

AbstractConfined volume systems, such as microdroplets, Leidenfrost droplets, or thin films, can accelerate chemical reactions. Acceleration occurs due to the evaporation of solvent, the increase in reactant concentration, and the higher surface-to-volume ratios amongst other phenomena. Performing reactions in confined volume systems derived from mass spectrometry ionization sources or Leidenfrost droplets allows for reaction conditions to be changed quickly for rapid screening in a time efficient and cost-saving manner. Compared to solution phase reactions, confined volume systems also reduce waste by screening reaction conditions in smaller volumes prior to scaling. Herein, the condensation of glyoxal with benzylamine (BA) to form hexabenzylhexaazaisowurtzitane (HBIW), an intermediate to the highly desired energetic compound 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), was explored. Five confined volume systems were compared to evaluate which technique was ideal for forming this complex cage structure. Substituted amines were also explored as BA replacements to screen alternative cage structure intermediates and evaluate how these accelerated techniques could apply to novel reactions, discover alternative reagents to form the cage compound, and improve synthetic routes for the preparation of CL-20. Ultimately, reaction acceleration is ideal for predicting the success of novel reactions prior to scaling up and determining if the expected products form, all while saving time and reducing costs. Acceleration factors and conversion ratios for each reaction were assessed by comparing the amount of product formed to the traditional bulk solution phase synthesis.

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Elisa preliminary studies of immobilization and specific detection of bacterial strains

Romanian Journal of Ecology & Environmental Chemistry ◽

10.21698/rjeec.2020.209 ◽

2020 ◽

Vol 2 (2) ◽

pp. 64-69

Author(s):

Madalina Mihalache ◽

◽

Alina Banciu ◽

Lucian Ionescu ◽

Mihai Nita-Lazar

Keyword(s):

Monoclonal Antibody ◽

Fluorescence Intensity ◽

Polyclonal Antibody ◽

Specific Binding ◽

Negative Control ◽

Enzyme Linked Immunosorbent Assay ◽

Bacterial Strains ◽

Specific Detection ◽

E Coli ◽

Alexa Fluor

The paper aims to emphasize the specific detection of bacterial strains using enzyme-linked immunosorbent assay. The assay is based on the specific binding of polyclonal antibody anti-E. coli tagged with FITC to E.coli and monoclonal antibody anti-Ps. aeruginosa tagged with Alexa Fluor 647 tagged to Ps. aeruginosa and on subsequent enzymatic immunological demonstration of the conjugated enzyme. In this experiment, the negative control was the Salmonella enterica strain. The two antibodies had no interaction with the negative control, instead, they were specific for E. coli and Ps. aeruginosa strains. When both strains were in the same well, the fluorescence intensity given by the presence of E. coli was 2.3 times higher than that given by Ps. aeruginosa, and the intensity of fluorescence decreased if there are both bacterial strains in the wells.

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Atmospheric Spectroscopy and Photochemistry at Environmental Water Interfaces

Annual Review of Physical Chemistry ◽

10.1146/annurev-physchem-042018-052311 ◽

2019 ◽

Vol 70 (1) ◽

pp. 45-69 ◽

Cited By ~ 10

Author(s):

J. Zhong ◽

M. Kumar ◽

J.M. Anglada ◽

M.T.C. Martins-Costa ◽

M.F. Ruiz-Lopez ◽

...

Keyword(s):

Atmospheric Aerosols ◽

Atmospheric Chemistry ◽

Environmental Water ◽

Bulk Solution ◽

Water Interface ◽

Atmospheric Species ◽

Theoretical Investigations ◽

Air Water Interface ◽

Phase Chemistry ◽

Interface Effects

The air–water interface is ubiquitous in nature, as manifested in the form of the surfaces of oceans, lakes, and atmospheric aerosols. The aerosol interface, in particular, can play a crucial role in atmospheric chemistry. The adsorption of atmospheric species onto and into aerosols modifies their concentrations and chemistries. Moreover, the aerosol phase allows otherwise unlikely solution-phase chemistry to occur in the atmosphere. The effect of the air–water interface on these processes is not entirely known. This review summarizes recent theoretical investigations of the interactions of atmosphere species with the air–water interface, including reactant adsorption, photochemistry, and the spectroscopy of reactants at the water surface, with an emphasis on understanding differences between interfacial chemistries and the chemistries in both bulk solution and the gas phase. The results discussed here enable an understanding of fundamental concepts that lead to potential air–water interface effects, providing a framework to understand the effects of water surfaces on our atmosphere.

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Precision Assessment of Biofluid Viscosity Measurements Using Molecular Rotors

Journal of Biomechanical Engineering ◽

10.1115/1.1894366 ◽

2005 ◽

Vol 127 (3) ◽

pp. 450-454 ◽

Cited By ~ 16

Author(s):

Walter J. Akers ◽

Mark A. Haidekker

Keyword(s):

Fluorescence Emission ◽

High Viscosity ◽

Plasma Viscosity ◽

Molecular Rotors ◽

Solution Viscosity ◽

Human Blood Plasma ◽

Fluid Viscosity ◽

Molecular Rotor ◽

Test Set ◽

Precision Assessment

Blood viscosity changes with many pathologic conditions, but its importance has not been fully investigated because the current methods of measurement are poorly suited for clinical applications. The use of viscosity-sensitive fluorescent molecular rotors to determine fluid viscosity in a nonmechanical manner has been investigated recently, but it is unknown how the precision of the fluorescence-based method compares to established mechanical viscometry. Human blood plasma viscosity was modulated with high-viscosity plasma expanders, dextran, pentastarch, and hetastarch. The samples were divided into a calibration and a test set. The relationship between fluorescence emission and viscosity was established using the calibration set. Viscosity of the test set was determined by fluorescence and by cone-and-plate viscometer, and the precision of both methods compared. Molecular rotor fluorescence intensity showed a power law relationship with solution viscosity. Mechanical measurements deviated from the theoretical viscosity value by less than 7.6%, while fluorescence-based measurements deviated by less than 6%. The average coefficient of variation was 6.9% (mechanical measurement) and 3.4% to 3.8% (fluorescence-based measurement, depending on the molecular rotor used). Fluorescence-based viscometry exhibits comparable precision to mechanical viscometry. Fluorescence viscometry does not apply shear and is therefore more practical for biofluids which have apparent non-Newtonian properties. In addition, fluorescence instrumentation makes very fast serial measurements possible, thus promising new areas of application in laboratory and clinical settings.

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Measurements of the timescales for the mass transfer of water in glassy aerosol at low relative humidity and ambient temperature

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4739-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 4739-4754 ◽

Cited By ~ 132

Author(s):

H.-J. Tong ◽

J. P. Reid ◽

D. L. Bones ◽

B. P. Luo ◽

U. K. Krieger

Keyword(s):

Mass Transfer ◽

Glass Transition ◽

Relative Humidity ◽

Gas Phase ◽

Mass Transfer Rate ◽

Solution Viscosity ◽

Bulk Solution ◽

Size Change ◽

Return To Equilibrium ◽

Kinetics Of

Abstract. The influence of glassy states and highly viscous solution phases on the timescale of aerosol particle equilibration with water vapour is examined. In particular, the kinetics of mass transfer of water between the condensed and gas phases has been studied for sucrose solution droplets under conditions above and below the glass transition relative humidity (RH). Above the glass transition, sucrose droplets are shown to equilibrate on a timescale comparable to the change in RH. Below the glass transition, the timescale for mass transfer is shown to be extremely slow, with particles remaining in a state of disequilibrium even after timescales of more than 10 000 s. A phenomenological approach for quantifying the time response of particle size is used to illustrate the influence of the glassy aerosol state on the kinetics of mass transfer of water: the time is estimated for the droplet to reach the halfway point from an initial state towards a disequilibrium state at which the rate of size change decreases below 1 nm every 10 000 s. This half-time increases above 1000 s once the particle can be assumed to have formed a glass. The measurements are shown to be consistent with kinetic simulations of the slow diffusion of water within the particle bulk. When increasing the RH from below to above the glass transition, a particle can return to equilibrium with the gas phase on a timescale of 10's to 100's of seconds, once again forming a solution droplet. This is considerably shorter than the timescale for the size change of the particle when glassy and suggests that the dissolution of the glassy core can proceed rapidly, at least at room temperature. Similar behaviour in the slowing of the mass transfer rate below the glass transition RH is observed for binary aqueous raffinose solution droplets. Mixed component droplets of sucrose/sodium chloride/water also show slow equilibration at low RH, illustrating the importance of understanding the role of the bulk solution viscosity on the rate of mass transfer with the gas phase, even under conditions that may not lead to the formation of a glass.

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Sensitive and selective determination of peptides, PG and PGP, using a novel fluorogenic reagent 4-chlorobenzene-1,2-diol

Chemical Papers ◽

10.1515/chempap-2015-0057 ◽

2015 ◽

Vol 69 (4) ◽

Cited By ~ 1

Author(s):

Hasina Yasmin ◽

Mohammed Shafikur Rahman ◽

Takayuki Shibata ◽

Tsutomu Kabashima ◽

Masaaki Kai

Keyword(s):

Reaction Time ◽

Linear Relationship ◽

Fluorescence Intensity ◽

Sodium Periodate ◽

Selective Detection ◽

Fluorometric Method ◽

Reaction Conditions ◽

Fluorescent Signal ◽

Selective Determination

AbstractA novel fluorometric method was developed for the sensitive and selective detection of Pro-Gly (PG) and Pro-Gly-Pro (PGP) using 4-chlorobenzene-1,2-diol (4-CBD) as a fluorogenic reagent. The reaction was performed at 37°C for 30 min in the presence of a borate buffer (pH 7.0) and sodium periodate. The resulting fluorescence intensity was measured using a spectrofluorometer with excitation and emission wavelengths of 450 nm and 535 nm. To obtain a stable fluorescent signal and maximise its intensity, different reaction conditions such as the concentrations of the reagents, the reaction time, and the pH were optimised. Under the optimised conditions, a linear relationship was obtained between fluorescence intensity and peptide concentrations from 1.0-40.0 μmol L

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Vectashield-induced fluorescence quenching hinders conventional and super resolution microscopy

10.1101/393264 ◽

2018 ◽

Author(s):

Aleksandra Arsić ◽

Nevena Stajković ◽

Rainer Spiegel ◽

Ivana Nikić-Spiegel

Keyword(s):

Fluorescence Intensity ◽

Fluorescent Dyes ◽

Super Resolution ◽

Practical Advice ◽

Alexa Fluor ◽

Stochastic Optical Reconstruction Microscopy ◽

Conventional Microscopy ◽

Optical Reconstruction ◽

The Right ◽

Super Resolution Microscopy

AbstractFinding the right combination of a fluorescent dye and a mounting medium is crucial for optimal microscopy of fixed samples. It was recently shown that Vectashield, one of the most commonly used mounting media for conventional microscopy, can also be applied to super-resolution direct stochastic optical reconstruction microscopy (dSTORM). dSTORM utilizes conventional dyes and starts with samples in a fluorescent ON state. This helps identifying structures of interests. Subsequently, labelled samples are brought to blinking, which is necessary for localization of single molecules and reconstruction of super-resolution images. This is only possible with certain fluorescent dyes and imaging buffers. One of the most widely used dyes for dSTORM, Alexa Fluor (AF) 647, blinks in Vectashield. However, after adding Vectashield to our samples, we noticed that the fluorescence intensity of AF647 and its improved variant, AF647+, is quenched. Since structures of interest cannot be identified in quenched samples, loss of fluorescence intensity hinders imaging of AF647 in Vectashield. This has consequences for both conventional and dSTORM imaging. To overcome this, we provide: 1) a quantitative analysis of AF647 intensity in different imaging media, 2) practical advice on how to use Vectashield for dSTORM imaging of AF647 and AF647+.

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Application of Trimethylsilanolate Alkali Salts in Organic Synthesis

Synthesis ◽

10.1055/s-0037-1609202 ◽

2018 ◽

Vol 50 (06) ◽

pp. 1199-1208 ◽

Cited By ~ 3

Author(s):

Jan Hlaváč ◽

Kristýna Bürglová

Keyword(s):

Alkali Metal ◽

Organic Synthesis ◽

Organic Solvents ◽

Solid Phase ◽

Chemical Transformations ◽

Organic Transformations ◽

Reaction Conditions ◽

Phase Chemistry ◽

Alkali Salts ◽

Solid Phase Chemistry

Trimethylsilanolate alkali salts are widely used in organic synthesis, mainly due to their solubility in common organic solvents. They are frequently used as nucleophiles in ester hydrolysis, both in solution and solid-phase chemistry. However, they have also been used as mild bases or as specific reagents in some chemical transformations. Reactions employing trimethylsilanolate alkali salts as the key component are typically performed under mild reaction conditions. This review summarizes the utilization of trimethylsilanolate alkali salts in various organic transformations.1 Introduction2 Properties of Alkali Metal Trimethylsilanolates (TMSO[M])3 Trimethylsilanolate Alkali Salts in Organic Synthesis4 Conclusion

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