Human axillary skin condition is improved following incorporation of glycerol into the stratum corneum from an antiperspirant formulation.

The study objectives were to demonstrate that glycerol, when topically applied from a roll-on antiperspirant formulation, can be delivered directly to human skin ex vivo and the axillary stratum corneum (SC) in vivo, and to assess whether it improves the quality of the axillary skin barrier. Ex vivo human skin absorption of glycerol was measured following application of a roll-on antiperspirant formulation containing 4% C-glycerol. Skin distribution of C-glycerol over 24 h was assessed using gas chromatography-mass spectrometry.

Confocal Raman spectroscopy of whole hairs.

This paper describes the application of Raman spectroscopy to whole hair fibers. Previously this has proved difficult because the hairs are relatively opaque, and spatial resolution diminishes with depth because of the change in refractive index. A solution is to couple confocal Raman with multivariate curve resolution (MCR) data analysis, which separates spectral differences with depth despite this reduction in resolution.

A new in vivo Raman probe for enhanced applicability to the body.

This paper describes a new in vivo Raman probe that allows investigation of areas of the body that are otherwise difficult to access. It is coupled to a previously described commercially available in vivo Raman spectrometer that samples the skin through an optical flat. In the work presented here, the laser light emerges from a smaller pen-shaped probe.

Using the fluorescence decay of 2-aminopurine to investigate conformational change in the recognition sequence of the EcoRV DNA-(adenine-N6)-methyltransferase on enzyme binding.

The EcoRV DNA methyltransferase methylates the first adenine in the GATATC recognition sequence. It is presumed that methylation proceeds by a nucleotide flipping mechanism but no crystal structure is available to confirm this. A popular solution-phase assay for nucleotide flipping employs the fluorescent adenine analogue, 2-aminopurine (2AP), substituted at the methylation target site; a substantial increase in fluorescence intensity on enzyme binding indicates flipping.

Dynamic in vivo mapping of model moisturiser ingress into human skin by GARfield MRI.

We describe the development of in vivo one-dimensional MRI (profiling) using a GARField (Gradient At Right angles to Field) magnet for the characterisation of side-of-hand human skin. For the first time and in vivo, we report measurements of the NMR longitudinal and transverse relaxation parameters and self-diffusivity of the upper layers of human skin with a nominal spatial resolution better than 10 µm. The results are correlated with in vivo confocal Raman spectroscopy measurements of water concentration and natural moisturiser factors, and discussed in terms of known skin biology and microstructure of the stratum corneum and viable epidermis.

On-chip, time-correlated, fluorescence lifetime extraction algorithms and error analysis.

A new, simple, and hardware-only fluorescence-lifetime-imaging microscopy (FLIM) is proposed to implement on-chip lifetime extractions, and their signal-to-noise-ratio based on statistics theory is also deduced. The results are compared with Monte Carlo simulations, giving good agreement. Compared with the commonly used iterative least-squares method or the maximum-likelihood-estimation- (MLE-) based, general purpose FLIM analysis software, our algorithm offers direct calculation of fluorescence lifetime based on the collected photon counts stored in on-chip counters and therefore delivers faster analysis for real-time applications, such as clinical diagnosis.

Long-wavelength fluorescence from 2-aminopurine-nucleobase dimers in DNA.

When 2-aminopurine (2AP) is substituted for adenine in DNA, it is widely accepted that its fluorescence spectrum is essentially unchanged from that of the free fluorophore. We show that 2AP in DNA exhibits long-wavelength emission and excitation bands, in addition to the familiar short-wavelength spectra, as a result of formation of a ground-state heterodimer with an adjacent, pi-stacked, natural base. The observation of dual emission from 2AP in a variety of oligodeoxynucleotide duplexes and single strands demonstrates the generality of this phenomenon.

Differential stabilization of reaction intermediates: specificity checkpoints for M.EcoRI revealed by transient fluorescence and fluorescence lifetime studies.

M.EcoRI, a bacterial sequence-specific S-adenosyl-L-methionine-dependent DNA methyltransferase, relies on a complex conformational mechanism to achieve its remarkable specificity, including DNA bending, base flipping and intercalation into the DNA. Using transient fluorescence and fluorescence lifetime studies with cognate and noncognate DNA, we have characterized several reaction intermediates involving the WT enzyme.

2-Aminopurine flipped into the active site of the adenine-specific DNA methyltransferase M.TaqI: crystal structures and time-resolved fluorescence.

We report the crystal structure of the DNA adenine-N6 methyltransferase, M.TaqI, complexed with DNA, showing the fluorescent adenine analog, 2-aminopurine, flipped out of the DNA helix and occupying virtually the same position in the active site as the natural target adenine. Time-resolved fluorescence spectroscopy of the crystalline complex faithfully reports this state: base flipping is accompanied by the loss of the very short ( approximately 50 ps) lifetime component associated with fully base-stacked 2-aminopurine in DNA, and 2-aminopurine is subject to considerable quenching by pi-stacking interactions with Tyr108 in the catalytic motif IV (NPPY).