Fluctuation-induced free energy of thin peptide films

Abstract

We apply the Lifshitz theory of dispersion forces to find a contribution to the free energy of peptide films which is caused by the zero-point and thermal fluctuations of the electromagnetic field.For this purpose, using available information about the imaginary parts of dielectric permittivity of peptides, the analytic representation for permittivity of typical peptide along the imaginary frequency axis is devised. Numerical computations of the fluctuation-induced free energy are performed at room temperature for the freestanding peptide films, containing different fractions of water, and for similar films deposited on dielectric (SiO 2 ) and (Au) substrates. It is shown that the free energy of a freestanding peptide film is negative and, thus, contributes to its stability.The magnitude of the free energy increases with increasing fraction of water and decreases with increasing thickness of a film. For peptide films deposited on a dielectric substrate the free energy is nonmonotonous. It is negative for thicker than 100 nm films, reaches the maximum value at some film thickness, but vanishes and changes its sign for thinner than 100 nm films. The fluctuation-induced free energy of peptide films deposited on metallic substrate is found to be positive which makes films less stable. In all three cases, simple analytic expressions for the free energy of sufficiently thick films are found. The obtained results may be useful to attain film stability in the next generation of organic microdevices with further shrinked dimensions.

Aggregation Properties of Albumin in Interacting with Magnetic Fluids

“…As already noted, the stability of molecular films has a critical effect on their applicability for the purposes of biomolecular electronics [ 29 , 70 , 74 , 75 ]. Since the current general trend towards the miniaturization of electronic components has led to the creation of thinner molecular films, the problem of their stability has become more urgent [ 76 , 77 ].…”

“…Since the current general trend towards the miniaturization of electronic components has led to the creation of thinner molecular films, the problem of their stability has become more urgent [ 76 , 77 ]. In previous work, the authors showed that as film thickness decreases, its stability is influenced by fluctuation forces [ 29 , 70 , 75 ]. The possibility of such an influence was predicted on the basis of previous studies [ 74 ].…”

“…To prepare the experimental samples, an aqueous solution of albumin in distilled water with a concentration of 50 mg/mL was used, because this is the minimum protein concentration required to achieve adhesion to an inorganic wettable substrate, which is significant for the creation of three-layer sandwich systems of the substrate–film–metal type for modeling and developing functional devices of biomolecular electronics [ 29 , 70 ].…”

“…Immobilized biomolecules with the addition of nanoparticles are often used to increase the speed, sensitivity, and selectivity of biomolecular devices, as well as to protect them against degradation [ 26 ]. Thus, the interaction processes of nanoparticles with biomolecules [ 27 ], as well as their effects on the activity preservation of the biological molecules immobilized on the electrode surfaces, require comprehensive study [ 28 , 29 ]. In our work, special attention was given to the study of hybrid materials based on biomolecules in combination with magnetic nanoparticles.…”

First-Principles Simulation of Dielectric Function in Biomolecules

“…Non-covalent dispersion van der Waals interactions are also thought to play an important role in protein folding [ 16 ] since they make a substantial contribution to protein–protein as well as protein–water interactions [ 17 ]. Additionally, in applications tied to organic optical and electronic devices as well as biotechnology, the contribution of van der Waals interactions to the stability of proteinaceous films deposited on a dielectric substrate has been recently noted [ 18 , 19 ].…”