Protein Film Formation Research Articles

On the existence of regular structures in liquid human blood serum (plasma) and phase transitions in the course of its drying

Experimental data show that regular three-dimensional liquid-crystal protein structures ranging in size from several hundredths to several tenths of a millimeter are present in the whole blood serum (plasma) of patients suffering from various diseases. When a drop of serum dries, some of the structures melt to produce a gel, whereas the rest of them undergo phase transition to form solid crystals. These crystals are shaped like immunoglobulin M molecules enlarged 1000-fold. In the serum (plasma) of ailing people, the amount of the gel formed upon drying increases, breaking the symmetry during the formation of nonequilibrium protein films. It is believed that low-intensity physical factors exert a therapeutic action by changing the phase state of protein in body fluids.

Chemical reactions in cottonseed protein cross-linking by formaldehyde, glutaraldehyde, and glyoxal for the formation of protein films with enhanced mechanical properties.

Amino acids involved in cottonseed protein cross-linking by formaldehyde, glutaraldehyde, and glyoxal during protein film formation were identified by an original technique. The entire HPLC amino acid profile (after acid hydrolysis) was studied, along with variations in reactive lysine contents, in films cross-linked or not with increasing quantities of formaldehyde, glutaraldehyde, and glyoxal. This strategy highlighted the formation of acid-resistant lysine derivatives that a simple reactive lysine determination would not have detected. The results-which agree with previously published data-enhance the overall understanding of cross-linking activities that occur in aqueous alkaline solutions during the formation of protein films made with cottonseed flour. Lysine was found to have a key role in protein cross-linking by dialdehydes, with the involvement of tyrosine in the presence of formaldehyde and of arginine in the presence of glyoxal. These results could provide valuable chemical tools for adjusting the mechanical properties of cottonseed protein films.

Recent Research Trends in Transglutaminase Technology for Food Processing.

Based on the hypothesis that cross-links contribute considerably to the physicochemical and functional properties of protein, we examined the usefulness of the cross-linking enzyme transglutaminase (TGase) in terms of protein polymerization, gelation, film formation, and peptide incorporation into protein. TGase-producing microorganisms were discovered, and mass production and preparation of the enzyme was accomplished. TGase has been used in the production of various new food items such as restructured meat and seafood, new textured sausages and fish cakes, retort resistant soybean curd, Iong-life noodles, volume-improved bread, etc. We present here an overview of developments in microbial TGase technology to date.

Real-Time Observation of Plasma Protein Film Formation on Well-Defined Surfaces with Scanning Force Microscopy

We report here the results of a scanning force microscopic (SFM) investigation into the structure of adsorbed bovine fibrinogen films on well-defined surfaces. SFM images show that a monolayer of fibrinogen assembles on both highly oriented pyrolytic graphite (HOPG) and mica. We find, however, that the film morphology varies as a function of the substrate. To unravel the nature of the observed differences, we tracked the growth of bovine fibrinogen layers at both surfaces in real-time. Consistent with the differences observed in the final film structure, we find that film formation on HOPG and mica proceeds through distinct mechanisms. A network is observed during fibrinogen film formation on HOPG, implying that protein−protein interactions are involved in the growth mechanism and likely govern the final film structure. The growth mechanism on mica proceeds by the homogeneous increase in the number of nuclei across the surface and gives no indication of significant intermolecular interactions. Surfactant ...

Contribution of convective flux to uniform apoferritin film formation on a liquid gallium surface

We generated nanometer thin apoferritin films on a liquid gallium surface by drying wetting films of aqueous apoferritin solution, which was formed continuously by expanding the solution. The film formation process had been optically visualized and then analyzed at different protein concentrations and expansion speed. We thus found that protein film formation consisted of protein adsorption to the surface coupled with a convective flux of proteins induced by water evaporation from the wetting film surface. We proved that a convective flux promoted film formation even if the included protein was in the nanometer-scale.

How to monitor the protein cross-linking by formaldehyde, glutaraldehyde or glyoxal in cotton-seed protein protein-based films? (short communication)

Cotton-seed protein-based films can be formed from an aqueous solution by a casting process. Chemical cross-linking treatments of cotton-seed proteins by dialdehyde increased maximum puncture force and decreased solubility of films in water. Glutaraldehyde, formaldehyde and glyoxal are cross-linking agents capable of reacting with amino acid side chains, particularly with the lysine ENH2 group, to form Schiff bases. As a first approach, simple criteria (maximum puncture force, puncture deformation, and film solubility) were used to assess the efficiency of chemical treatments. In the present study the amount of lysine that did not react with cross-linking agents (reactive lysine) during cotton-seed protein film formation was used to assess the degree of protein cross-linking. We have used a new procedure that provide a quantitative determination of reactive lysine in films made from cotton-seed flour. Subsequently, this methodology was used to investigate the cross-linking of cotton-seed proteins by formaldehyde, glutaraldehyde or glyoxal in films and to analyse the relation between protein cross-linking and film maximum puncture force

Interfacial Aggregation of Bovine Serum Albumin Related to Crystallization Conditions Studied by Total Internal Reflection Fluorescence

Total internal reflection fluorescence (TIRF) was used to examine adsorption and interfacial aggregation of bovine serum albumin (BSA) from solvent conditions that are known to promote BSA crystallization. In the absence of a crystallizing agent (thermodynamically good solvent conditions), adsorption from a 0.1 mg/mL BSA solution in 50 mM phosphate buffer, pH 6.2, 25°C, results in formation of not more than monolayer protein films on both hydrophilic and hydrophobic surfaces. However, in the presence of ammonium sulfate, which is used as an agent to crystallize BSA, adsorption yields a relatively thick multilayer protein film. The interfacial aggregation is sensitive to hydrophobicity of the substrate as well as to the prehistory of adsorption. A hydrophilic substrate promotes formation of thicker protein films than a hydrophobic one. For example, in the presence of 2.13 M ammonium sulfate, BSA adsorption during ∼10 h yields approximately a 20-monolayer film on the quartz surface, in contrast to a 6–7 monolayer film on the hydrophobic surface. Rates of multilayer adsorption and desorption and the ultimate thickness of the multilayer protein film critically depend on the concentration of crystallizing agent. The rates correlate with the osmotic second virial coefficient,B22, which has been shown to be a predictor for protein crystallization. In the range ofB22values known as a “crystallization slot,” the multilayer adsorption demonstrates a uniform rate of film growth. Noncrystallizing solvents do not exhibit this feature. The TIRF technique can be used to investigate molecular mechanisms of crystal growth and growth cessation as well as epitaxial and pseudoepitaxial growth using protein crystals grown at or attached to the surface. TIRF provides a sensitive and powerful tool to probein situand in real time the interactions of dissolved protein with a growing protein solid phase.

Effect of chloride salts on protein extraction and interfacial protein film formation in meat batters

AbstractSix comminuted chicken breast meat mixes and six meat batters were made with isoionic NaCl (25 g kg−1), MgCl2, CaCl2, KCl, LiCl (IS = 0.43) and 15 g kg−1 NaCl (IS = 0.26). The quantity and type of proteins extracted and used for interfacial protein film (IPF) formation was determined and related to batter stability. The monovalent salts produced IPF which differed in individual protein content between salts but which all contained significantly larger amounts of protein (P < 0.01) than those using divalent salts. MgCl2 extracted more protein than CaCl2 and produced a different protein profile in the IPF. However, MgCl2 formed unstable raw batters whereas CaCl2 did not. In addition, a simple, rapid method for extracting and quantifying proteins from meat batters was developed to assist in direct determination of the actual soluble protein uptake by the fat phase during comminution.

Gluten formation studied by the transmission electron microscope

The structure of gluten and its formation was investigated by transmission electron microscopy. Stretching the strands of the native framework of insoluble endosperm protein levels down globular surface structures to form a platelet-like arrangement on protein sheets. Treating the sheets with solutions of triethylamine or dithioerythritol results in an increased appearance of thread-like forms, which are considered to be one of the structural elements of gluten. The formation of gluten is basically a process of aggregation and of the mechanical transformation of materials that exist in the pre-formed state within the endosperm cells. The most important transformation is the formation of protein films, which starts at the branching points of protein strands and results in a layer-like arrangement in dough and gluten.

Ultrastructure of denaturated potato proteins

AbstractThe structure of potato protein precipitates formed by heat treatment or acidification of potato juice was investigated by transmission electron microscopy. Precipitates formed by heat denaturation (3 min at 100°C) consist of electron‐dense particles of diameter < 300 nm, aggregated into three‐dimensional open networks. Precipitates, formed by acidification to pH 3.0 and holding the acidified juice at room temperature, consist of network‐like aggregates of electron‐dense particles embedded in thin films which hinder the formation of a dense sediment. This structure explains the high sediment volumes which are typical of this kind of precipitate. By warming the acidified potato juice to 40°C, rapid flocculation and sedimentation of the suspended insoluble protein are observed within a few minutes and a dense sediment is finally obtained. This sediment consists mainly of the network‐like aggregates of electron‐dense particles and material of low electron density formed by the collapse of the films. Protein films have also been observed in precipitates of heat‐denatured bovine serum albumin (BSA). High‐methoxyl pectin promotes the formation of protein films on heat denaturation of potato proteins or BSA.

STUDIES IN AGGLUTINATION

FROM THE FOREGOING EVIDENCE, SPECIFIC BACTERIAL AGGLUTINATION MAY BE CONCEIVED OF AS FOLLOWS: When bacteria are mixed with their homologous agglutinative sera, specific union between organism and agglutinin occurs. This interaction consists of specific coating of the bacteria by globulin. By virtue of the fact, noted by Loeb and illustrated in Fig. 6, that protein film formation gives the coated particle the characteristics of denatured protein, the bacteria now take on the character of particles of denatured globulin. Particles of denatured protein flocculate whenever their charge is reduced by electrolyte to a critical level lying somewhere between 12 and 14 millivolts. This is true even when the salt is strong, as, unlike bacterial particles, their cohesive force is not readily depressed by salt. The sensitized bacteria, now being essentially particles of denatured protein, likewise agglutinate as soon as their charge is reduced by electrolyte to this potential level.