HIV as a chronic disease.

The 25th anniversary of the first reports of a catastrophic illness later classified as AIDS and the 10th anniversary of highly active antiretroviral therapy (HAART) both occurred in 2006. Where available, HAART has revolutionised the treatment of HIV. This success has brought challenges--the unknown long-term history of treated HIV infection, the development of toxicity and drug resistance, and the ageing HIV-infected patient.

Peptide adsorption to lipid bilayers: slow processes revealed by linear dichroism spectroscopy.

The adsorption and insertion kinetics for the association of two 34-residue cyclic peptides with phosphocholine membranes have been studied using circular and linear dichroism approaches. The two peptides studied are identical with the exception of two residues, which are both tyrosine in one of the peptides and tryptophan in the other. Both peptides adopt random coil conformations in solution in the absence of membranes and do not aggregate at concentrations below 20 microM.

How to study DNA and proteins by linear dichroism spectroscopy.

The technique of linear dichroism (LD) is a simple absorbance technique that uses two polarised light beams. Since only oriented molecules show different absorbances for different polarisations, LD detects only oriented molecules. In aqueous solutions, flow orientation is an attractive orientation methodology as it selects long molecules or molecular assemblies.

Antimicrobial activity of an iron triple helicate.

The prevalence of antibiotic resistance has resulted in the need for new approaches to be developed to combat previously easily treatable infections. Here we investigated the potential of the synthetic metallomolecules [Fe(2)L(3)](4+) and [Cu(2)(L')(2)](2+) as antibacterial agents. Both molecules have been shown to bind DNA; [Fe(2)L(3)](4+) binds in the major groove and causes DNA coiling, whilst [Cu(2)(L')(2)](2+) can act as an artificial nuclease.

Ruthenium polypyridyl complexes and their modes of interaction with DNA: is there a correlation between these interactions and the antitumor activity of the compounds?

Various interaction modes between a group of six ruthenium polypyridyl complexes and DNA have been studied using a number of spectroscopic techniques. Five mononuclear species were selected with formula [Ru(tpy)L(1)L(2)]((2-n)+), and one closely related dinuclear cation of formula [{Ru(apy)(tpy)}(2){mu-H(2)N(CH(2))(6)NH(2)}](4+). The ligand tpy is 2,2':6',2''-terpyridine and the ligand L(1) is a bidentate ligand, namely, apy (2,2'-azobispyridine), 2-phenylazopyridine, or 2-phenylpyridinylmethylene amine.

Breaking the 200 nm limit for routine flow linear dichroism measurements using UV synchrotron radiation.

The first synchrotron radiation flow linear dichroism spectra are reported. High-quality spectral data can be collected from 450 nm down to 180 nm in contrast to the practical cutoff of approximately 200 nm on benchtop instruments. State-of-the-art microvolume capillary Couette flow linear dichroism was successfully ported to a synchrotron radiation source.

Folding and membrane insertion of the pore-forming peptide gramicidin occur as a concerted process.

Many antibiotic peptides function by binding and inserting into membranes. Understanding this process provides an insight into the fundamentals of both membrane protein folding and antibiotic peptide function. For the first time, in this work, flow-aligned linear dichroism (LD) is used to study the folding of the antibiotic peptide gramicidin.

Cluster of falciparum malaria cases in UK airport.

A cluster of 6 cases of Plasmodium falciparum malaria occurred in a UK airport among 30 travelers returning to the United States from East Africa. Molecular genotyping analysis indicated that all had been exposed to different parasites. The travelers' use of chemoprophylaxis was poor; their perception of risk was limited.

DNA binding and bending by dinuclear complexes comprising ruthenium polypyridyl centres linked by a bis(pyridylimine) ligand.

The interaction of enantiomerically pure dinuclear complexes of the form [Ru2(L-L)4L1]4+ (where L-L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and L1 = bis(pyridylimine) ligand ((C5H4N)CN(C6H4))2CH2)) with ct-DNA have been investigated by absorbance, circular dichroism, fluorescence displacement assays, thermal analysis, linear dichroism and gel electrophoresis. The complexes all bind more strongly to DNA than ethidium bromide, stabilise DNA and have a significant bending effect on DNA. The data for Delta,Delta-[Ru2(bpy)4L1]4+ are consistent with it binding to DNA outside the grooves wrapping the DNA about it.

A new reference material for UV-visible circular dichroism spectroscopy.

To obtain accurate and consistent measurements from circular dichroism (CD) instruments over time and from different laboratories, it is important that they are properly calibrated. The characteristics of the available reference materials are not ideal to ensure proper calibration as they typically only give peaks in one or two spectral regions, and often have issues concerning purity and stability. Currently either camphor sulfonic acid or ammonium camphor sulfonate are used.

Synthesis and cytotoxicity of dinuclear complexes containing ruthenium(II) bipyridyl units linked by a bis(pyridylimine) ligand.

Enantiopure dinuclear ruthenium polypyridyl complexes of the form [Ru(2)(LL)(4)L(1)](PF(6))(4) (LL = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen); L(1)= C(25)H(20)N(4) a bis(pyridylimine) ligand containing a diphenylmethane spacer) have been synthesized using the chiral building blocks cis-[Ru(bpy)(2)(py)(2)](2+) and cis-[Ru(phen)(2)(py)(2)](2+). These dinuclear ruthenium complexes have been characterised using NMR, mass spectrometry, UV-visible absorbance, circular dichroism and linear dichroism. The compounds exhibit good photo and thermal stability.

Influence of surface shape on DNA binding of bimetallo helicates.

In order to probe the DNA-helicate interactions responsible for the DNA binding and remarkable changes of the DNA secondary structure induced by a tetracationic bi-metallo helicate [Fe(2)(L(1))(3)](4+) (L(1)=C(25)H(20)N(4)), we have designed and synthesised derivatives with hydrophobic methyl groups at different positions on the ligand backbone. Two dimetallo helicates [Fe(2)(L(i))(3)](4+) were prepared using ligands L(3) and L(5) with the methyl substituent on, respectively, the 3 and 5 positions of the pyridyl ring thus producing a wider or slightly longer tetracationic DNA binder. UV/visible absorbance, circular and linear dichroism spectroscopies have been used to characterize the interactions of the cylinders with DNA with the aim of investigating any sequence preference or selectivity upon binding.

DNA binding studies of a new dicationic porphyrin. Insights into interligand interactions.

Cationic porphyrins have an affinity for DNA and potential for applications in the fields of photodynamic therapy and cellular imaging. This report describes a new dicationic porphyrin, 5,15-dimethyl-10,20-di(N-methylpyridinium-4-yl)porphyrin, abbreviated H2tMe2D4. Although tetrasubstituted, H2tMe2D4 presents modest steric requirements and forms in reasonable yield by a "2+2" synthetic method.

Design and non-covalent DNA binding of platinum(II) metallacalix[4]arenes.

A set of cyclic tetranuclear complexes of the metallacalix[4]arene type with formula [{Pt(en)(L)}(4)](4+) (en=ethylenediamine; 2: LH=5-chloro-2-hydroxypyrimidine (5-Cl-Hpymo); 3: LH=5-bromo-2-hydroxypyrimidine (5-Br-Hpymo); 4: LH=5-iodo-2-hydroxypyrimidine (5-I-Hpymo)) have been obtained from the reaction between cis-protected square-planar [Pt(en)(H(2)O)(2)](2+) metal entities and LH in aqueous media. Additionally, the binding properties of 2, 3, 4 and their congener [{Pt(en)(L)}(4)](4+) (1: LH=2-hydroxypyrimidine (Hpymo)) with calf thymus-DNA (ct-DNA) have been studied by using different techniques including circular and linear dichroism (CD and LD, respectively) and UV-visible absorbance spectroscopies, gel electrophoresis, fluorescence competitive-binding studies and atomic force microscopy (AFM). The results are consistent with significant non-covalent interactions taking place between the polynuclear cyclic species and ct-DNA.

Circular and linear dichroism of proteins.

Circular dichroism (CD) is an important technique in the structural characterisation of proteins, and especially for secondary structure determination. The CD of proteins can be calculated from first principles using the so-called matrix method, with an accuracy which is almost quantitative for helical proteins. Thus, for proteins of unknown structure, CD calculations and experimental data can be used in conjunction to aid structure analysis.

FtsZ polymer-bundling by the Escherichia coli ZapA orthologue, YgfE, involves a conformational change in bound GTP.

Cell division is a fundamental process for both eukaryotic and prokaryotic cells. In bacteria, cell division is driven by a dynamic, ring-shaped, cytoskeletal element (the Z-ring) made up of polymers of the tubulin-like protein FtsZ. It is thought that lateral associations between FtsZ polymers are important for function of the Z-ring in vivo, and that these interactions are regulated by accessory cell division proteins such as ZipA, EzrA and ZapA.

Synthetic metallomolecules as agents for the control of DNA structure.

This tutorial review summarises B-DNA structure and metallomolecule binding modes and illustrates some DNA structures induced by molecules containing metallic cations. The effects of aquated metal ions, cobalt amines, ruthenium octahedral metal complexes, metallohelicates and platinum complexes such as cis-platin are discussed alongside the techniques of NMR, X-ray crystallography, gel electrophoresis, circular dichroism, linear dichroism and molecular dynamics. The review will be of interest to people interested in both DNA structure and roles of metallomolecules in biological systems.

Enantiomeric resolution of supramolecular helicates with different surface topographies.

The enantiomeric resolution of an extended range of di-metallo supramolecular triple-helical molecules are reported. The ligands for all complexes are symmetric with two units containing an aryl group linked via an imine bond to a pyridine. Alkyl substituents have been attached in different positions on the ligand backbone.

Structural characterisation of the insecticidal toxin XptA1, reveals a 1.15 MDa tetramer with a cage-like structure.

A recently identified class of proteins conferring insecticidal activity to several bacteria within the Enterobacteriaceae family have potential for control of commercially important insect pests. Here, we report the first purification, biophysical characterisation and 3-D structural analysis of one of the toxin components, XptA1, from Xenorhabdus nematophila PMFI296 to a resolution of 23 A. Membrane binding studies indicate that the three-component toxin system has a different mode of action from that of proteins from Bacillus thuringiensis (Bt).

Contributions of hydroxyethyl groups to the DNA binding affinities of anthracene probes.

Contributions of hydroxyethyl functions to the DNA binding affinities of substituted anthracenes are evaluated by calorimetry and spectroscopy. Isothermal titration calorimetry indicated that binding of the ligands to calf thymus DNA (5 mM Tris buffer, 50 mM NaCl, pH 7.2, 25 degrees C) is exothermic.

Shape effects on the activity of synthetic major-groove binding ligands.

In this work we present the results of a molecular simulation study of two different tetracationic bis iron(II) supramolecular cylinders interacting with DNA. One cylinder has been shown to bind in the major groove of DNA and to induce dramatic coiling of the DNA; the second is a derivative of the first, with additional methyl groups attached so as to give a larger cylinder-radius. The simulations show that both cylinders bind strongly to the major groove of the DNA, and induce complex structural changes in A-T rich regions.

Improved curve fitting procedures to determine equilibrium binding constants.

For ligand-biomacromolecule titration experiments it has been traditional practice to extract parameters such as the equilibrium binding constant K and the number of bases per ligand binding site n with relatively labour intensive methods, usually based on single wavelength data, such as the difference method by Rodger and Nordén coupled together with a Scatchard plot. Presented in this paper are both the theory and a least squares fitting method to derive parameters such as K and n more directly from all spectral non-linear experimental data. Both the case of non competitive binding of a metal complex ligand to DNA and the case of displacement by a metal complex ligand of an ethidium marker attached to the DNA are considered.

Looking at long molecules in solution: what happens when they are subjected to Couette flow?

Knowing the structure of a molecule is one of the keys to deducing its function in a biological system. However, many biomacromolecules are not amenable to structural characterisation by the powerful techniques often used namely NMR and X-ray diffraction because they are too large, or too flexible or simply refuse to crystallize. Long molecules such as DNA and fibrous proteins are two such classes of molecule.

An estrogen-platinum terpyridine conjugate: DNA and protein binding and cellular delivery.

A platinum metal complex in which terpyridine joins estradiol (via an ethynyl link) to a platinum with a labile ligand (chloride) has been designed, synthesised and its X-ray crystal structure determined. The aim of this work was to link a targeting motif (in this case estrogen) to a metal-based biomolecule recognition unit (the platinum moiety). The target molecule: 17alpha-[4'-ethynyl-2,2':6',2'-terpyridine]-17beta-estradiol platinum(II) chloride (PtEEtpy) has been shown to bind to both human and bovine serum albumin (SA) and to DNA.

Restriction enzyme kinetics monitored by UV linear dichroism.

The use of linear dichroism (LD) spectroscopy for biological applications has been brought to the forefront recently by our development of thermostated microvolume Couette cells. We present a method for following the digestion of DNA by restriction endonucleases in real time without the use of any extrinsic dyes or labels. This is accomplished using linear dichroism spectroscopy (the differential absorbance of light polarized parallel and perpendicular to the sample orientation axis).