Can the Isothermal Calorimetric Curve Shapes Suggest the Structural Changes in Micellar Aggregates?

Inspired by the unusual shapes of the titration curve observed for many surfactants and mixed colloidal systems, we decided to extend the analysis to isothermal titration calorimetric curves (ITC) by paying special attention to potential structural changes in micellar aggregates. In this paper, we used isothermal titration calorimetry in conjunction with Scanning Transmission Electron Microscopy (STEM), Small-Angle Neutron Scattering (SANS) and X-ray Scattering (SAXS) methods support by Monte Carlo and semiempirical quantum chemistry simulations to confirm if the isothermal calorimetric curve shape can reflect micelle transition phenomena. For that purpose, we analysed, from the thermodynamic point of view, a group of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethylalkylammonium) bromides. We proposed the shape of aggregates created by surfactant molecules in aqueous solutions and changes thereof within a wide temperature range. The results provide evidence for the reorganization processes and the relationship (dependence) between the morphology of the created aggregates and the conditions such as temperature, surfactant concentration and spacer chain length which affect the processes.

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Solvation dynamics and rotational relaxation of coumarin 153 in mixed micelles of Triton X-100 and cationic gemini surfactants: effect of composition and spacer chain length of gemini surfactants

Physical Chemistry Chemical Physics ◽

10.1039/c5cp03835a ◽

2016 ◽

Vol 18 (3) ◽

pp. 1551-1563 ◽

Cited By ~ 13

Author(s):

Sonu Sonu ◽

Sunita Kumari ◽

Subit K. Saha

Keyword(s):

Chain Length ◽

Gemini Surfactant ◽

Mixed Micelles ◽

Gemini Surfactants ◽

Rotational Relaxation ◽

Solvation Dynamics ◽

Cationic Gemini Surfactants ◽

Coumarin 153 ◽

Spacer Chain Length ◽

Triton X

To demonstrate simultaneously how the solvation dynamics and rotational relaxation in nonionic micelles change with the composition of a gemini surfactant and how this change depends on spacer chain length of gemini surfactants.

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A study of α-cyclodextrin with a group of cationic gemini surfactants utilizing isothermal titration calorimetry and NMR

The Journal of Chemical Thermodynamics ◽

10.1016/j.jct.2005.08.010 ◽

2006 ◽

Vol 38 (6) ◽

pp. 773-777 ◽

Cited By ~ 10

Author(s):

De-Zhi Sun ◽

Xiao-Mei Qiu ◽

Ling Li ◽

Xi-Lian Wei ◽

Bao-Lin Yin

Keyword(s):

Isothermal Titration Calorimetry ◽

Gemini Surfactants ◽

Titration Calorimetry ◽

Cationic Gemini Surfactants

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Design of a UHV STEM for Through-The-Lens Electron Spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135502 ◽

1990 ◽

Vol 48 (2) ◽

pp. 380-381

Author(s):

A. J. Bleeker ◽

P. Kruit

Keyword(s):

Secondary Electron ◽

High Vacuum ◽

Secondary Electron Emission ◽

Auger Spectroscopy ◽

Scanning Transmission Electron Microscope ◽

Point Of View ◽

Ultra High Vacuum ◽

Scanning Transmission ◽

Auger Spectra ◽

Coincidence Measurements

Combining of the high spatial resolution of a Scanning Transmission Electron Microscope and the wealth of information from the secondary electrons and Auger spectra opens up new possibilities for materials research. In a prototype instrument at the Delft University of Technology we have shown that it is possible from the optical point of view to combine STEM and Auger spectroscopy [1]. With an Electron Energy Loss Spectrometer attached to the microscope it also became possible to perform coincidence measurements between the secondary electron signal and the EELS signal. We measured Auger spectra of carbon aluminium and Argon gas showing energy resolutions better than 1eV [2]. The coincidence measurements on carbon with a time resolution of 5 ns yielded basic insight in secondary electron emission processes [3]. However, for serious Auger spectroscopy, the specimen needs to be in Ultra High Vacuum. ( 10−10 Torr ). At this moment a new setup is in its last phase of construction.

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Influence of Ascorbic Acid on the Structure and Function of Alpha-2- macroglobulin: Investigations using Spectroscopic and Thermodynamic Techniques

Protein and Peptide Letters ◽

10.2174/0929866526666191002113525 ◽

2020 ◽

Vol 27 (3) ◽

pp. 201-209

Author(s):

Syed Saqib Ali ◽

Mohammad Khalid Zia ◽

Tooba Siddiqui ◽

Haseeb Ahsan ◽

Fahim Halim Khan

Keyword(s):

Ascorbic Acid ◽

Conformational Changes ◽

Structural Changes ◽

The Body ◽

Titration Calorimetry ◽

Spectroscopic Techniques ◽

Human Beings ◽

Plasma Ascorbic Acid ◽

Dietary Antioxidant ◽

And Function

Background: Ascorbic acid is a classic dietary antioxidant which plays an important role in the body of human beings. It is commonly found in various foods as well as taken as dietary supplement. Objective: The plasma ascorbic acid concentration may range from low, as in chronic or acute oxidative stress to high if delivered intravenously during cancer treatment. Sheep alpha-2- macroglobulin (α2M), a human α2M homologue is a large tetrameric glycoprotein of 630 kDa with antiproteinase activity, found in sheep’s blood. Methods: In the present study, the interaction of ascorbic acid with alpha-2-macroglobulin was explored in the presence of visible light by utilizing various spectroscopic techniques and isothermal titration calorimetry (ITC). Results: UV-vis and fluorescence spectroscopy suggests the formation of a complex between ascorbic acid and α2M apparent by increased absorbance and decreased fluorescence. Secondary structural changes in the α2M were investigated by CD and FT-IR spectroscopy. Our findings suggest the induction of subtle conformational changes in α2M induced by ascorbic acid. Thermodynamics signatures of ascorbic acid and α2M interaction indicate that the binding is an enthalpy-driven process. Conclusion: It is possible that ascorbic acid binds and compromises antiproteinase activity of α2M by inducing changes in the secondary structure of the protein.

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Interbase-FRET binding assay for pre-microRNAs

Scientific Reports ◽

10.1038/s41598-021-88922-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Mattias Bood ◽

Anna Wypijewska del Nogal ◽

Jesper R. Nilsson ◽

Fredrik Edfeldt ◽

Anders Dahlén ◽

...

Keyword(s):

Ligand Binding ◽

Drug Targets ◽

Structural Changes ◽

Small Sample Size ◽

Resonance Energy ◽

Small Sample ◽

Titration Calorimetry ◽

Drug Candidate ◽

Binding Studies ◽

Aberrant Expression

AbstractThe aberrant expression of microRNAs (miRs) has been linked to several human diseases. A promising approach for targeting these anomalies is the use of small-molecule inhibitors of miR biogenesis. These inhibitors have the potential to (i) dissect miR mechanisms of action, (ii) discover new drug targets, and (iii) function as new therapeutic agents. Here, we designed Förster resonance energy transfer (FRET)-labeled oligoribonucleotides of the precursor of the oncogenic miR-21 (pre-miR-21) and used them together with a set of aminoglycosides to develop an interbase-FRET assay to detect ligand binding to pre-miRs. Our interbase-FRET assay accurately reports structural changes of the RNA oligonucleotide induced by ligand binding. We demonstrate its application in a rapid, qualitative drug candidate screen by assessing the relative binding affinity between 12 aminoglycoside antibiotics and pre-miR-21. Surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) were used to validate our new FRET method, and the accuracy of our FRET assay was shown to be similar to the established techniques. With its advantages over SPR and ITC owing to its high sensitivity, small sample size, straightforward technique and the possibility for high-throughput expansion, we envision that our solution-based method can be applied in pre-miRNA–target binding studies.

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