Zoltan Blum

Chapter 3 – Molecular Forces and Self-Assembly

This Chapter outlines the nature, delicacy, and specificity of molecular forces, and the ways these forces work together with the geometry of molecules to organize self-assembled molecular aggregates. It discusses the meaning of the size and shape of a molecule and describes the forces that enable the curvature of aggregates of self assembled molecules to be changed. The acute sensitivity of many biological phenomena to temperature can in some cases be correlated with forces. A brief overview of ideas and the physical notions behind self-assembly of surfactant-water systems is presented. The classical intuition on molecular forces is embodied in the Derjaguin–Landau–Verwey–Overbeek theory of colloid stability. It blends two themes: (1) an intervening liquid can be thought of as a structureless continuum with bulk liquid properties, up to a molecular distance from the surface and (2) any object (surface) must perturb proximal liquid structure (density, dipolar orientation, and hydrogen bonding) so that the transmission of force is propagated via a stress field passing from molecule to molecule in much the same way that the electromagnetic field is carried through the vacuum or a dielectric in Maxwells theory of the electromagnetic field.

TEM-tomography of FAU-zeolite crystals containing Pt-clusters.

A method for preparing ultrathin sections (- 20 nm) of inorganic solids has been developed using ultramicrotomy of resin-embedded crystal fragments. Undamaged crystals, oriented along a crystallographic direction, could be imaged with transmission electron microscopy (TEM) at a resolution better than 0.5 nm. The true internal structure of the crystals could be investigated by imaging the second in a series of at least three consecutive ultrathin sections. Such TEM-tomography proved that Pt-ion exchanged FAU zeolite crystals, after reduction and oxidation, are occupied internally and randomly of large platinum clusters mainly in the {111-twin planes. TEM-tomography could be useful in man made nanostructures like semiconductors, epitaxial thin films, hard metal coatings, ceramics, catalysts, and biomaterials.

BEHAVIORAL OBSERVATIONS AND MEASUREMENTS OF AERIAL PHEROMONE IN A MATING DISRUPTION TRIAL AGAINST PEA MOTH Cydia nigricana F. (LEPIDOPTERA, TORTRICIDAE)

Synthetic sex pheromone of the pea mothCydia nigricana. (E,E)-8,10-dodecadien-1-yl acetate (E8,E10–12 : Ac), was applied in a 3-ha pea field at a rate of 17 g/ha, in two different dispenser formulations. Aerial concentrations within pea canopy, as determined by a field electroantennogram (EAG) apparatus, were 2 and 3 ng/m3 in the two dispenser treatments. The validity of the EAG measurements was corroborated by sampling of field air, followed by gas chromatographic quantification ofE8,E10–12 : Ac. Males were attracted to fresh dispensers releasingE8,E10–12 : Ac plus less than 2% of the antagonisticE, Z; Z, E; andZ, Z isomers. Two days after placement, the proportion of these isomers had increased to 6%. Males were then no longer attracted to the dispensers, but were observed to fly out of the treated field. Male attraction to calling females was almost entirely suppressed, and attraction to traps baited with synthetic pheromone was significantly reduced. Larval infestation in the pheromone-treated field was 2%, compared to 36% in a control field.

The platinum agglomeration in the {111}-twin planes of the zeolite FAU

Abstract The preferred location of platinum clusters in the {111}-twin planes (TP) of zeolite NaY (FAU) has been observed by high-resolution transmission electron microscopy (HRTEM). The platinum was incorporated in the zeolite by ion exchange followed by oxidation and reduction. Samples from each of the three different synthesis stages were examined by HRTEM. Ion exchange provides a homogeneous platinum distribution in the zeolite, and agglomeration of platinum in the TP was only observed after the oxidation. The HRTEM observations of platinum in the TP, from two independent directions, 〈110〉 and 〈211〉, support the fact that the platinum clusters are intrazeolitic. HRTEM observations of ultrathin sections (

Utilization of zeolite Y in the removal of anionic, cationic and nonionic detergents during purification of proteins

Hydrophobie zeolite Y was used to adsorb detergents from protein solutions and within one minute the commonly used detergents sodium dodecyl sulfate, cetyl trimethyl ammonium bromide, and Triton X-100 at concentrations of 10 mg/ml were adsorbed to a level below their critical micelle concentrations. From the detergent depleted solutions 77 to 85 % of the proteins were recovered; the lower value was obtained with protein concentration below one mg/ml.

The density of silicon-rich zeolite frameworks

Many low-density frameworks containing channel networks (such as zeolites) are related to periodic minimal surfaces of well characterized surface area. This observation allows a direct connection to be made between the framework density and the average size of rings in the framework that lie on the hyperbolic surface. The analysis exploits the observation that the area per vertex on the surfaces is the same as that for related uncurved sheet silicates, which implies that the density of the framework can be inferred from the average ring size alone. The relation between density and bond lengths and angles is also discussed. A lower bound for the density of open-framework silicates and hydrophobic zeolites is suggested that is consistent with the preferred bonding geometry of SiO 2 networks

Chapter 1 – The Mathematics of Curvature

This chapter reviews some of the mathematical tools that are required to describe special properties of curved surfaces. The tools are to be found in differential geometry, analytical function theory, and topology. A particular class of saddleshaped (hyperbolic) surfaces called “minimal surfaces” is treated with special attention because they are relatively straightforward to treat mathematically and do form good approximate representations of actual physical and chemical structures. The principal curvatures can be combined to give two useful measures of the curvature of the surface: the Gaussian curvature (K) and the mean curvature (H). The Gaussian curvature has a number of interesting geometrical interpretations. One of the more striking is connected with the Gauss map of a surface, which maps the surface onto the unit sphere. The Gauss-Bonnet theorem is a profound theorem of differential geometry, linking global and local geometry. A minimal surface can be represented (locally) by a set of three integrals. They represent the inverse of a mapping from the minimal surface to a Riemann surface. The P-surface, the D-surface, and the gyroid are the simplest members of a large family of structures whose members are still being identified. In many ways these three surfaces are the most important; they have been identified in a variety of physical systems, from silicates to cells.

Chapter 8 – Some Miscellaneous Speculations

This chapter discusses the role of curvature in templating and in inorganic condensed systems and mentions a class of more complicated supra-assembled aggregates. It also discusses a role for curvature in the origin of life itself. Templating generally refers to the process whereby a molecular form is constructed from a pattern set by a (templating) molecule. However, a more subtle form of templating may be responsible for the atomic arrangement of many structures, from silicates to organic cryptate molecules. In these cases, the atomic structure of the templated species is set by the electric field of the templating material, rather than the physical surface of the template. For certain arrangements of the templating material, the field lines traversing the volume lie on a variety of unusual hyperbolic geometries, close to those of minimal surfaces. The crystallization of zeolites invariably requires the presence of templating species. A wide variety of templates have been used from sodium ions, tetra-alkyl ammonium ions to crown ethers.

Chapter 4 – Beyond Flatland: The Geometric Forms due to Self-Assembly

This chapter describes surface structures where curved forms are spontaneously adopted by aggregates of simple macromolecules. These can range from synthetic surfactants and natural lipids (typically about 20A in length) to synthetic copolymers and proteins (1000A). The analysis includes both natural and synthetic molecules because lipids and proteins can be considered as more complex counterparts of surfactants and block co-polymers. The effect of molecular shape on aggregation geometry is also described, along with a brief discussion on the theory of self-assembly of chiral molecules. Two characteristics determine the shape of molecular aggregates. First is the shape of the constituent molecules, which sets the curvature of the aggregate. Second is coupled to the chirality of the molecules, which also determines the curvature of the aggregate via the geodesic torsion. The interfacial geometry is characterized by two distinct signatures: (1) the interfacial curvatures, which describe its local geometry and (2) the interfacial topology, which describes global geometry, including the connectivity of the interface.

Chapter 6 – Folding and Function In Proteins and DNA

The chemical and topological complexity of proteins is most conveniently communicated using a sequence of structural descriptors. The primary structure deals only with the protein molecule as a one-dimensional string—the succession of amino acids along that string. The peptide sequence spontaneously winds into regular clusters of sheets or helices at certain locations along its length; these are features of its secondary structure. At a still larger length scale, the twists and turns of the molecular thread fold into a tertiary structure of the molecule. Subsequent self-assembly of protein molecules gives the quaternary structure. As a consequence of the individual order of the amino acids and the conformation of the ensuing polypeptide strands (the primary and secondary structures) the three-dimensional structure of each molecule (its tertiary structure) is formed. A fundamental feature of proteins is their amphiphilic and chiral characteristics, which induce folding of the peptide chain that results in a mainly hydrophobic core covered by a hydrophilic surface layer. In the evolution of protein structure, which has taken place in an aqueous environment, the forces that drive self- assembly have played a central role.