Plasma membrane properties involved in the photodynamic efficacy of merocyanine 540 and tetrasulfonated aluminum phthalocyanine

Merocyanine 540 (MC540)-mediated photodynamic damage to erythrocytes was strongly reduced when illumination was performed at pH 8.5 as compared to pH 7.4. This could be explained by high pH-mediated hyperpolarization of the erythrocyte membrane, resulting in decreased MC540 binding at pH 8.5. In accordance, the MC540-mediated photooxidation of open ghosts was not inhibited at pH 8.5. Photoinactivation of vesicular stomatitis virus (VSV) was not inhibited at pH 8.5. This suggests that illumination at increased pH could be an approach to protect red blood cells selectively against MC540-mediated virucidal phototreatment. With tetrasulfonated aluminum phthalocyanine (AIPcS4) as photosensitizer, damage to erythrocytes, open ghosts and VSV was decreased when illuminated at pH 8.5. A decreased singlet oxygen yield at high pH could be excluded. The AIPcS4-mediated photooxidation of fixed erythrocytes was strongly dependent on the cation concentration in the buffer, indicating that the surface potential may affect the efficacy of this photosensitizer. This study showed that altering the environment of the target could increase both the efficacy and the specificity of a photodynamic treatment.     

The combinatorics and extreme value statistics of protein threading

In protein threading, one is given a protein sequence, together with a database of protein core structures that may contain the natural structure of the sequence. The object of protein threading is to correctly identify the structure(s) corresponding to the sequence. Since the core structures are already associated with specific biological functions, threading has the potential to provide biologists with useful insights about the function of a newly discovered protein sequence. Statistical tests for threading results based on the theory of extreme values suggest several combinatorial problems. For example, what is the number of waysm′=# _t {L _i >x _i } _i ⁼⁰ⁿ of choosing a sequence {X _i } _i ⁼¹ⁿ from the set {1, 2, ...,t}, subject to the difference constraints {L _i =X _i+1?X _i >x _i } _i ⁼⁰ⁿ , whereX ₀=0,X _n+1=t+1, and {x _i } _i ⁼⁰ⁿ is an arbitrary sequence of integers? The quantitym′ has many attractive combinatorial interpretations and reduces in special continuous limits to a probabilistic formula discovered by the Finetti. Just as many important probabilities can be derived from de Finetti's formula, many interesting combinatorial quantities can be derived fromm′. Empirical results presented here show that the combinatorial approach to threading statistics appears promising, but that structural periodicities in proteins and energetically unimportant structure elements probably introduce statistical correlations that must be better understood.     

Algebras of Symmetric Holomorphic Functions on lp

The authors study the algebra of uniformly continuous holomorphicsymmetric functions on the ball of l_p, investigating in particularthe spectrum of such algebras. To do so, they examine the algebraof symmetric polynomials on l_p-spaces, as well as finitely generatedsymmetric algebras of holomorphic functions. Such symmetricpolynomials determine the points in l_p up to a permutation.     

Graphene growth on h-BN by molecular beam epitaxy

The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated. Formation of single-layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands. Atomic-force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h-BN substrates. The growth is governed by the high mobility of the carbon atoms on the h-BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms.     

The Bishop-Phelps-Bollobás theorem for operators

We prove the Bishop-Phelps-Bollobás theorem for operators from an arbitrary Banach space X into a Banach space Y whenever the range space has property β of Lindenstrauss. We also characterize those Banach spaces Y for which the Bishop-Phelps-Bollobás theorem holds for operators from ?₁ into Y. Several examples of classes of such spaces are provided. For instance, the Bishop-Phelps-Bollobás theorem holds when the range space is finite-dimensional, an L₁(μ)-space for a σ-finite measure μ, a C(K)-space for a compact Hausdorff space K, or a uniformly convex Banach space.     

Convex vector lattices and l-algebras

For A an Archimedean Riesz space (=vector lattice) with distinguished positive weak unit e_A, we have the Yosida representation  as a Riesz space in D(X_A), the lattice of extended real valued functions on the space of e_A-maximal ideas. This note is about those A for which  is a convex subset of D(X_A); we call such A “convex”.Convex Riesz spaces arise from the general issue of embedding as a Riesz ideal, from consideration of uniform- and order-completeness, and from some problems involving comparison of maximal ideal spaces (which we won't discuss here; see [10]).The main results here are: (2.4) A is convex iff A is contained as a Riesz ideal in a uniformly complete Φ-algebra B with identity e_A. (3.1) Any A has a convex reflection (i.e., embeds into a convex B with a universal mapping property for Riesz homomorphisms; moreover, the embedding is epic and large).     

Left–right and dynamic correlation

Within density functional theory, it is natural to separate the correlation energy into two parts: left–right correlation and dynamic correlation. Left–right correlation arises from the exchange part of functionals, and dynamic correlation arises from the correlation part of functionals. We examine the nature of these correlation energies as molecules are distorted. We observe that such a natural separation is not possible using the methods of quantum chemistry. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Stereochemistry of post-transition metal oxides: revision of the classical lone pair model

The chemistry of post transition metals is dominated by the group oxidation state N and a lower N-2 oxidation state, which is associated with occupation of a metal s(2) lone pair, as found in compounds of Tl(I), Pb(II) and Bi(III). The preference of these cations for non-centrosymmetric coordination environments has previously been rationalised in terms of direct hybridisation of metal s and p valence orbitals, thus lowering the internal electronic energy of the N-2 ion. This explanation in terms of an on-site second-order Jahn-Teller effect remains the contemporary textbook explanation. In this tutorial review, we review recent progress in this area, based on quantum chemical calculations and X-ray spectroscopic measurements. This recent work has led to a revised model, which highlights the important role of covalent interaction with oxygen in mediating lone pair formation for metal oxides. The role of the anion p atomic orbital in chemical bonding is key to explaining why chalcogenides display a weaker preference for structural distortions in comparison to oxides and halides. The underlying chemical interactions are responsible for the unique physicochemical properties of oxides containing lone pairs and, in particular, to their application as photocatalysts (BiVO(4)), ferroelectrics (PbTiO(3)), multi-ferroics (BiFeO(3)) and p-type semiconductors (SnO). The exploration of lone pair systems remains a viable a venue for the design of functional multi-component oxide compounds.