1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

The glue proteins secreted by marine mussels bind strongly to virtually all inorganic and organic surfaces in aqueous environments in which most adhesives function poorly. Studies of these functionally unique proteins have revealed the presence of the unusual amino acid 3,4-dihydroxy-L-phenylalanine (dopa), which is formed by posttranslational modification of tyrosine. However, the detailed binding mechanisms of dopa remain unknown, and the chemical basis for mussels' ability to adhere to both inorganic and organic surfaces has never been fully explained. Herein, we report a single-molecule study of the substrate and oxidation-dependent adhesive properties of dopa. Atomic force microscopy (AFM) measurements of a single dopa residue contacting a wet metal oxide surface reveal a surprisingly high strength yet fully reversible, noncovalent interaction. The magnitude of the bond dissociation energy as well as the inability to observe this interaction with tyrosine suggests that dopa is critical to adhesion and that the binding mechanism is not hydrogen bond formation. Oxidation of dopa, as occurs during curing of the secreted mussel glue, dramatically reduces the strength of the interaction to metal oxide but results in high strength irreversible covalent bond formation to an organic surface. A new picture of the interfacial adhesive role of dopa emerges from these studies, in which dopa exploits a remarkable combination of high strength and chemical multifunctionality to accomplish adhesion to substrates of widely varying composition from organic to metallic.

https://www.pnas.org/content/pnas/103/35/12999.full.pdf

Single-molecule mechanics of mussel adhesion

Colloid mobilization and transport in groundwater

The extensible byssal threads of marine mussels are shielded from abrasion in wave-swept habitats by an outer cuticle that is largely proteinaceous and approximately fivefold harder than the thread core. Threads from several species exhibit granular cuticles containing a protein that is rich in the catecholic amino acid 3,4-dihydroxyphenylalanine (dopa) as well as inorganic ions, notably Fe3+. Granular cuticles exhibit a remarkable combination of high hardness and high extensibility. We explored byssus cuticle chemistry by means of in situ resonance Raman spectroscopy and demonstrated that the cuticle is a polymeric scaffold stabilized by catecholato-iron chelate complexes having an unusual clustered distribution. Consistent with byssal cuticle chemistry and mechanics, we present a model in which dense cross-linking in the granules provides hardness, whereas the less cross-linked matrix provides extensibility.

/pdf/iron-clad-fibers-a-metal-based-biological-strategy-for-hard-346vhy0jte.pdf

Iron-Clad Fibers: A Metal-Based Biological Strategy for Hard Flexible Coatings

Adhesion of polymers

Effect of oxidation rate on cross-linking of mussel adhesive proteins

Adhesion between polymeric phases like adhesives and plastic surfaces is critical in many technological and industrial applications. In the last decades much progress has been made to understand the impact of the surface properties of both phases on the adhesive strength between them. These surface properties influence processes like wetting, molecular adsorption and inter-diffusion which determine how an interface develops into an interphase after the two materials have been brought into contact. Ultimately, the properties of this interphase determine the overall adhesion strength of an assembly. In this paper important parameters in the adhesion process will be reviewed, including methods to engineer these parameters in order to attain adhesion strengths ranging from complete release to irreversible bonding.

Surface Properties of Plastic Materials in Relation to Their Adhering Performance

On the basis of experimental observations described earlier, we have proposed that marginal regeneration is caused by surface tension gradients at the borders of mobile foam films. Marginal regeneration is the rate-determining mechanism in the drainage of such films, and, as such, a determining factor in the persistence (or long-term stability) of foams. Marangoni flows are caused by surface tension gradients, and these set off the exchange of thicker for thin film elements along the borders, while the total film area remains the same. In this paper we present simulations of the drainage of liquid in a vertical soap film, and show that it is realistic to expect large surface tension gradients along the lower border of the film under the conditions which lead to marginal regeneration. Copyright 1999 Academic Press.

Marginal regeneration and the Marangoni effect

How to develop globular proteins into adhesives.

A new and simple method is described to plate silicon structures with metallic silver for ultralarge-scale integration in dimensions down to 100 nm at an aspect ratio of 4.25. The silver deposition is initiated by an exchange reaction of silicon with silver ions, and the subsequent layer growth of the activated wafers occurs by electroless plating from supersaturated aqueous silver salt solutions at pH ∼ 11. No extra reducing agents are needed since silver ions are reduced at the catalytic silver surface by hydroxyl ions. The spontaneous ion-metal transition only proceeds at pH ∼ 11 and is likely mediated by the formation of subnanometer-sized [Ag 4 (OH) 2 ] 2+ clusters. The silver plating proceeds more easily in smaller structures and yields void-free, crystallized deposits.

Gert Frens

Papers

Effect of oxidation rate on cross-linking of mussel adhesive proteins

Surface Properties of Plastic Materials in Relation to Their Adhering Performance

Marginal regeneration and the Marangoni effect

How to develop globular proteins into adhesives.

Electroless Silver Deposition in 100 nm Silicon Structures