Rapid at-line pharmaceutical cleaning verification using a novel light induced fluorescence (LIF) sensor.

A novel light emitting diode (LED) array-based light induced fluorescence (LIF) sensor is presented as an analytical methodology for at-line cleaning verification within the pharmaceutical industry. This sensor differs from conventional LIF sensors through the ability to dynamically control both the LED excitation array and detection parameters, enabling the exploitation of the optical power and detection sensitivity to rapidly detect trace concentrations of residual drug. This feature makes this sensor an ideal alternative to conventional cleaning verification analytical methodologies.

The UV-absorption spectrum of human iridal melanosomes: a new perspective on the relative absorption of eumelanin and pheomelanin and its consequences.

Photoemission electron microscopy is used to measure the absorption coefficients, εc, of intact iridal stroma melanosomes isolated from dark brown and blue-green human irides for the spectral range λ=244-310 nm. These iridal stroma melanosomes were chosen because different colored irides produce organelles of varying eumelanin:pheomelanin ratios with similar size and morphology. Similar absorption spectra are found for the two types of melanosomes.

The effect of hydration on the UV absorption coefficient of intact melanosomes.

The physical properties of melanosomes have been shown to depend on water content. Herein, the ultraviolet absorption coefficient at λ = 244 nm for intact bovine choroidal melanosomes is determined from photoemission electron microscopy images recorded as a function of vacuum exposure. The dehydration of the melanosome under ultra-high vacuum manifests itself by a decrease in the absorption coefficient to about 60% of its initial value, and a concomitant increase in its image brightness.

UV-absorption spectra of melanosomes containing varying 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid content.

Central to understanding the photochemical properties of melanosomes is a direct measurement of their absorption coefficients. Herein, the absorption spectra of intact melanosomes of varying molecular compositions and embryonic origins were measured and compared over the spectral range from 245 to 310 nm. The absorption spectra of melanosomes predominately comprised of the eumelanin pigment were found to differ significantly from their constituent precursor molecules, 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA).

The red and the black.

"Pigmentation, which is primarily determined by the amount, the type, and the distribution of melanin, shows a remarkable diversity in human populations, and in this sense, it is an atypical trait."--E. J.

The ultraviolet absorption coefficient of melanosomes decreases with increasing pheomelanin content.

Uveal melanosomes from the iridal stroma contain both eumelanin and pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at lambda = 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/pheomelanin ratio of 14.

Direct measurement of the ultraviolet absorption coefficient of single retinal melanosomes.

A novel approach to photoemission electron microscopy is used to enable the first direct measurement of the absorption coefficient from intact melanosomes isolated from bovine retinal pigment epithelial cells. The difference in absorption between newborn and adult melanosomes is in good agreement with that predicted from the relative amounts of the monomeric precursors present in the constituent melanin as determined by chemical degradation analyses. The results demonstrate that for melanosomes containing eumelanins, there is a direct relation between the absorption coefficient and the relative 5,6-dihydroxyindole: 5,6-dihydroxyindole-2-carboxylic acid (DHI:DHICA) content, with an increased UV absorption coefficient associated with increasing DHICA content.

Human iridal stroma melanosomes of varying pheomelanin contents possess a common eumelanic outer surface.

Uveal melanosomes originating in the iridal stroma contain both black (eumelanin) and red (pheomelanin) pigment. Recent studies reveal that the eumelanin/pheomelanin ratio varies with iris color, with lower ratios being observed for lighter color (hazel, blue) irides. This is of great interest because the epidemiology of uveal melanomas also indicates an increased incidence for lighter-colored irides.

Challenges in applying photoemission electron microscopy to biological systems.

Photoemission electron microscopy (PEEM) is a unique surface-sensitive instrument capable of providing real-time images with high spatial resolution. While similar to the more common electron microscopies, scanning electron microscopy and transmission electron microscopy, the imaging technology relies on the photogeneration of electrons emitted from a sample through light excitation. This imaging technique has found prominence in surface and materials sciences, being well suited for imaging flat surfaces, and changes that occur to that surface as various parameters are changed (e.

Insights into melanosomes and melanin from some interesting spatial and temporal properties.

Melanosomes are organelles found in a wide variety of tissues throughout the animal kingdom and exhibit a range of different shapes: spheres of up to approximately 1 mum diameters and ellipsoids with lengths of up to approximately 2 mum and varying aspect ratios. The functions of melanosomes include photoprotection, mitigation of the effects of reactive oxygen species, and metal chelation. The melanosome contains a variety of biological molecules, e.

Multidimensional tunneling in the [1,5] shift in (Z)-1,3-pentadiene: how useful are Swain-Schaad exponents at detecting tunneling?

Rates, kinetic isotope effects (KIE), and Swain-Schaad exponents (SSE) have been calculated for a variety of isotopologues for the [1,5] shift in (Z)-1,3-pentadiene using mPW1K/6-31+G(d,p). Quantum mechanical effects along the reaction coordinate were incorporated with the zero-curvature tunneling (ZCT) model and with the multidimensional small curvature tunneling (SCT) model, which allows for coupling of modes perpendicular to the reaction coordinate. The latter model gives the best agreement with experimental rates and primary KIEs.