Aggregation behavior of giant amphiphiles prepared by cofactor reconstitution

We report on biohybrid surfactants, termed "giant amphiphiles", in which a protein or an enzyme acts as the polar head group and a synthetic polymer as the apolar tail. It is demonstrated that the modification of horseradish peroxidase (HRP) and myoglobin (Mb) with an apolar polymer chain through the cofactor reconstitution method yields giant amphiphiles that form spherical aggregates (vesicles) in aqueous solution. Both HRP and Mb retain their original functionality when modified with a single polystyrene chain, but reconstitution has an effect on their activities. In the case of HRP the enzymatic activity decreases and for Mb the stability of the dioxygen myoglobin (oxy-Mb) complex is reduced, which is probably the result of a disturbed binding of the heme in the apo-protein or a reduced access of the substrate to the active site of the enzyme or protein.     

Photocount distribution of photons emitted from three sites of a human body

Spontaneous photon emission from 30 sites on the skin of a live human subject is measured at different times and on different days. Signals from three representative sites of low, intermediate and high intensities are selected for further analysis. Fluctuations in these signals are measured by the probabilities of detecting different numbers of photons in a bin. The probabilities have non-classical features and are well described by the signal in a quantum squeezed state of photons. Measurements with bins of three sizes yield same values of three parameters of the squeezed state. A procedure for making correction due to background noise is developed. The correction changes the parameters of the quantum state. The new state appears more like a coherent state of photons.     

A comparison of vowel normalization procedures for language variation research

An evaluation of vowel normalization procedures for the purpose of studying language variation is presented. The procedures were compared on how effectively they (a) preserve phonemic information, (b) preserve information about the talker's regional background (or sociolinguistic information), and (c) minimize anatomical/physiological variation in acoustic representations of vowels. Recordings were made for 80 female talkers and 80 male talkers of Dutch. These talkers were stratified according to their gender and regional background. The normalization procedures were applied to measurements of the fundamental frequency and the first three formant frequencies for a large set of vowel tokens. The normalization procedures were evaluated through statistical pattern analysis. The results show that normalization procedures that use information across multiple vowels ("vowel-extrinsic" information) to normalize a single vowel token performed better than those that include only information contained in the vowel token itself ("vowel-intrinsic" information). Furthermore, the results show that normalization procedures that operate on individual formants performed better than those that use information across multiple formants (e.g., "formant-extrinsic" F2-F1).     

Tunable command layers for liquid crystal alignment

A simple method for the construction of a stable, tunable, self-assembled command layer for liquid crystal display purposes is described. A pyridine-functionalized oligosiloxane spontaneously forms an anisotropic, grooved surface on indium-tin-oxide, enabling it to align liquid crystalline molecules. The pyridine functions act as seeds for the epitaxial growth of stacks of highly ordered zinc phthalocyanines, the height of which can be controlled. These stacks increase the interaction between the surface and the liquid crystalline matrix by amplifying the surface ordering into the liquid crystal bulk. By varying the height of the stacks, direct control over the properties of the liquid crystal domains is achieved. These properties can be further tuned by adding to the liquid crystal, micro- and nanomolar concentrations of nitrogen-containing compounds, which are capable of interacting with and dissolving the stacks. The procedures we describe offer possibilities to use such tunable systems in LCD-based sensor devices as well as in solar-cell applications.     

Chiral molecular tapes from novel tetra(thiafulvalene-crown-ether)-substituted phthalocyanine building blocks

A tetra(thiafulvalene-crown-ether) phthalocyanine self-assembles into helical tapes nanometers wide and micrometers long. Formation of these scrolled molecular architectures is a first for phthalocyanine fibres and shows potential as a novel conducting material.     

Solid phase synthesis of biohybrid block copolymers

A new versatile route to synthesise biohybrid block copolymers is presented in which an amine terminated polymer is attached to an aldehyde functionalised resin, from which in subsequent steps the desired peptide can be grown using standard procedures.     

Highly negative homotropic allosteric binding of viologens in a double-cavity porphyrin

The synthesis of a double-cavity porphyrin with interesting allosteric binding properties toward viologens (N,N'-disubstituted 4,4'-bipyridines) is described. The porphyrin host forms very strong 1:2 complexes with viologens, displaying a negative allosteric behavior. The first viologen guest binds exceptionally tight (K > 107 M-1), and the second guest binds much more weakly (DeltaDeltaG = 9-15 kJ mol-1). The allosteric effect, one of the highest reported so far, originates in structural changes upon binding the first ligand, closely following the sequential (or induced-fit) theory of allosteric interactions by Koshland, Némethy, and Filmer (the KNF-model).