K. S. Birdi

Bio: K. S. Birdi is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Adsorption & Desorption. The author has an hindex of 3, co-authored 5 publications receiving 238 citations.

Lipid and Biopolymer Monolayers at Liquid Interfaces

Abstract: 1. Introduction.- 2. Thermodynamics of Liquid Surfaces.- 3. Experimental Methods and Procedures in Monolayers.- 4. Lipid Monolayers at Liquid Interfaces.- 5. Biopolymer (Protein) and Synthetic Polymer Monolayers.- 6. Kinetics of Adsorption and Desorption.- 7. Lipid-Protein Monolayers.- 8. Monolayers of Membrane Proteins.- 9. Adsorption of Monolayers on Solids (Langmuir-Blodgett Films).- 10. Diverse Applications of Monomolecular Films.- References.

Kinetics of Adsorption and Desorption

Abstract: The surface tension of water decreases when an amphiphile molecule, such as alcohol or protein, adsorbs at the air-water or oil-water interface. The adsorption is determined by the energy barriers that oppose both the removal of the polar hydroxyl group from the water phase and the entry of the hydrophobic alkyl group into the aqueous medium. The kinetics by which the alcohol molecule comes close to the interface are determined by the diffusion process alone. On the other hand, the kinetics of desorption of the alcohol monolayer are related to quite a high energy barrier. The same holds true for polymers, although in this case conformation (kinetics of conformation changes) and molecular weight are added parameters.

Lipid Monolayers at Liquid Interfaces

Abstract: In living systems, the structures of the cells and tissues are based on large molecules—proteins, polysaccharides, and complex lipids—while the organization of the systems appears to be a function of the nucleic acid complexes. Most lipid molecules are not as complex or as large as proteins. A large variety of compounds exist, many of them differing only in the composition of the long-chain fatty acid or aldehyde moieties. The word “lipid” (from the Greek lipos,“fat”) covers what seems to be an everexpanding group of compounds, the classification of which has been a subject of some controversy.

Biopolymer (Protein) and Synthetic Polymer Monolayers

Abstract: The adsorption of an amphiphile molecule at the water interface is ascribed to the alkyl part being attracted to the interface. It therefore becomes imperative to determine what kind of interfacial forces could be present in the case of molecules more complex than those of lipids, such as biopolymers (e.g., proteins, synthetic polyamino acids), synthetic polymers, and other polymers, such as cellulose. In the same context, it is of interest to determine whether any comparisons can be made between simple lipidlike molecules and biopolymers. Because of the great importance of biopolymers in everyday life, there exists a vast literature on the physical properties of biopolymers in solution. On the other hand, the interfacial properties of these biopolymers have not been investigated as extensively as they deserve to be.

Lipid-Protein Monolayers

Abstract: The importance of studying mixtures of lipids and proteins in monomolecular films is obvious when one considers the currently accepted fluid mosaic model of membranes (Fig. 7.1) (Singer, 1971, 1974; Singer and Nicolson, 1972). The classic Danielli-Dayson lipid bilayer (Gorter and Grendel, 1925; Danielli and Dayson, 1935) functions in its liquid crystalline phase transition region. Furthermore, it was realized many decades ago that the diversity in chemical composition and functional specialization of membranes presents a formidable obstacle in assigning a specific functional role to each of the membrane components, e.g., lipids and proteins. It has been suggested that the lipid bilayer functions as a protein solvent with solvent domains in equilibrium with lipid domains (Papahadjopoulos et al., 1973). Phase or domain fluctuations, possibly regulating membrane function, can be related to localized energy fluctuations of approximately kT (≈ 2400 J ≈ 600 cal) or to localized protein perturbations resulting from a change in protein conformation.

Ostwald Ripening and Related Phenomena

Abstract: Ostwald ripening in multicomponent systems is discussed in terms of thermodynamic stability and metastability. While the insoluble species trapped in the bulk of the drops can provide thermodynamic stability, only metastability is possible when the species is trapped at the interface between the phases. Similarly, a Helfrich-type dependence of the surface tension on curvature can produce metastability, but not thermodynamic stability. When the drops are encapsulated with a cross-linked permeable membrane, or with an insoluble surfactant monolayer, the membrane must be able to withstand the stress of the Laplace pressure and not collapse; this condition is in general hard to implement unless the emulsion drops are small, ∼10–100 nm. The effect of micelles on various mass transfer processes in surfactant systems, such as Ostwald ripening, composition ripening, adsorption from micellar solutions, and solubilization kinetics are discussed. Two mechanisms are possible: In the first, micelles fuse directly with...

Fluid Films with Curvature Elasticity

Abstract: The phenomenology of surfactant fluid-film microstructures interspersed in bulk fluids poses significant challenges to continuum theory. By using simple models of elastic surfaces, chemical physicists have been partially successful in describing the qualitative features of ...

Effects of Hofmeister anions on DPPC Langmuir monolayers at the air-water interface

Abstract: In this work we investigated the effect of sodium salts of different monovalent anions belonging to the Hofmeister series on Langmuir monolayers of DPPC (1,2-dipalmitoyl phosphatidylcholine). The salts used were NaCl, NaBr, NaNO3, NaI, NaBF4, NaClO4, and NaSCN. The monolayer phase behavior and the morphology and structure of the lipid phases were studied by surface pressure−area isotherms, Brewster Angle Microscopy (BAM), Grazing Incidence X-ray Diffraction (GIXD), and Infrared Reflection−Absorption Spectroscopy (IRRAS). The presence of electrolytes in the subphase was found to increase the surface pressure at a fixed area per molecule, indicating a stabilization of the liquid-expanded phase of the monolayer. This increase is different for different anions and different electrolyte concentrations. X-ray diffraction and infrared spectroscopy experiments show that moderate concentrations of chaotropic anions, such as I-, do not significantly change the conformation and packing properties of the hydrocarbon ...