Unique evolution of Vitamin A as an external pigment in tropical starlings

Pigments are largely responsible for the appearance of organisms. Most biological pigments derive from the metabolism of shikimic acid (melanins), mevalonic acid (carotenoids) or levulinic acid (porphyrins), which thus generate the observed diversity of external phenotypes. Starlings are generally dark birds despite iridescence in feathers, but 10% of species have evolved plumage pigmentation comprising bright colors that are known to be produced only by carotenoids. However, using micro-Raman spectroscopy, we have discovered that the bright yellow plumage coloration of one of these species, the Afrotropical golden-breasted starling Cosmopsarus regius, is not produced by carotenoids, but by vitamin A (all-trans-retinol). This is the first organism reported to deposit significant amounts of vitamin A in its integument and use it as a body pigment. Phylogenetic reconstructions reveal that the retinol-based pigmentation of the golden-breasted starling has independently appeared in the starling family from dark ancestors. Our study thus unveils a unique evolution of a new class of external pigments consisting of retinoids.Peer Reviewe

LC-MS determination of catecholamines and related metabolites in red deer urine and hair extracted using magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite

A novel analytical methodology for the extraction and determination of catecholamines (dopamine, epinephrine and norepinephrine) and their metabolites DL-3,4-dihydroxyphenyl glycol and DL-3,4-dihydroxymandelic acid by LC-MS is developed and validated for its application to human and animal urine and hair samples. The method is based on the preliminary extraction of the analytes by a magnetic multi-walled carbon nanotube poly(styrene-co-divinylbenzene) composite. This is followed by a 90%. Accuracy values comprised the range 79.5-109.5% when the analytes were extracted from deer urine samples using the selected MMWCNT-poly(STY-DVB) sorbent. This methodology was applied to real red deer urine and hair samples, and concentrations within range from 0.05 to 0.5 µg mL-1 for norepinephrine and from 1.0 to 44.5 µg mL-1 for its metabolite 3,4-dihydroxyphenyl glycol were calculated. Analyses of red deer hair resulted in high amounts of 3,4-dihydroxyphenyl glycol (0.9-266.9 µg mL-1)

Detection of Porphyrins in Hair Using Capillary Liquid Chromatography-Mass Spectrometry

Unlike humans, some animals have evolved a physiological ability to deposit porphyrins, which are pigments produced during heme synthesis in cells, in the skin and associated integument such as hair. Given the inert nature and easiness of collection of hair, animals that present porphyrin-based pigmentation constitute unique models for porphyrin analysis in biological samples. Here we present the development of a simple, rapid, and efficient analytical method for four natural porphyrins (uroporphyrin I, coproporphyrin I, coproporphyrin III and protoporphyrin IX) in the Southern flying squirrel Glaucomys volans, a mammal with hair that fluoresces and that we suspected has porphyrin-based pigmentation. The method is based on capillary liquid chromatography-mass spectrometry (CLC-MS), after an extraction procedure with formic acid and acetonitrile. The resulting limits of detection (LOD) and quantification (LOQ) were 0.006–0.199 and 0.021–0.665 μg mL−1, respectively. This approach enabled us to quantify porphyrins in flying squirrel hairs at concentrations of 3.6–353.2 μg g−1 with 86.4–98.6% extraction yields. This method provides higher simplicity, precision, selectivity, and sensitivity than other methods used to date, presenting the potential to become the standard technique for porphyrin analysis.The Spanish Ministry of Science and Innovation, JJCC Castilla—La Mancha and University of Castilla—La Mancha are gratefully acknowledged for funding this work with Grants PID2019-104381GB-I00, JCCM SBPLY/17/180501/000262 and 2020-GRIN-28882, respectively.Peer reviewe

Pheomelanin subunit non-destructive quantification by Raman spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS)

To date no direct methods are available for the subunit quantification of pheomelanin, the sulfur-containing melanin form whose structure increases melanoma risk. Here we apply Raman spectroscopy combined with chemometrics (MCR-ALS method) to quantify benzothiazine (BT) and benzothiazole (BZ), the constituent monomers of pheomelanin. The Raman spectra of synthetic pheomelanins only composed of BT or BZ were markedly different from those of natural pheomelanins composed of mixed BT-BZ, indicating the necessity of using a multivariate curve resolution method to extract the pure profiles of these monomers in complex samples. MCR-ALS with correlation constraint was applied to the Raman spectra of pheomelanized feathers from 26 bird species to predict BT-BZ concentrations. The methodology was able to quantify BT with R ​= ​0.91 and a relative error of 9%, for the range of 100–1000 ​ng/mg. However, the model did not perform well for BZ quantification. In addition, the MCR-ALS model could retrieve a pure profile associated to keratin, a major component (interference) in feathers. The deconvolution of Raman spectra, which predicts total pheomelanin content, combined with MCR-ALS, which predicts BT content, can therefore provide a complete pheomelanin determination at the monomeric level. This represents a direct and non-destructive analytical method for pheomelanin subunits, opening the door to investigate the differential cytotoxicity of these subunits in a high diversity of biological samples, including melanoma.A. C. O. N. thanks the Brazilian entity Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior for financial support (PNPD/CAPES).M. Z. and A. R. gratefully acknowledge financial support from the Spanish Ministry of Science and Innovation (PID2019-104381 GB-I00), Junta de Comunidades de Castilla-La Mancha (SBPLY/17/180501/000262) and University of Castilla-La Mancha (2020-GRIN-28882)Peer reviewe

Unprecedented high catecholamine production causing hair pigmentation after urinary excretion in red deer

Hormones have not been found in concentrations of orders of magnitude higher than nanograms per milliliter. Here, we report urine concentrations of a catecholamine (norepinephrine) ranging from 0.05 to 0.5 g/l, and concentrations of its metabolite dl-3,4-dihydroxyphenyl glycol (DOPEG) ranging from 1.0 to 44.5 g/l, in wild male red deer Cervus elaphus hispanicus after LC–MS analyses. The dark ventral patch of male red deer, a recently described sexually selected signal, contains high amounts of DOPEG (0.9–266.9 mg/l) stuck in the hairs, while DOPEG is not present in non-darkened hair. The formation of this dark patch is explained by the chemical structure of DOPEG, which is a catecholamine-derived o-diphenol susceptible to be oxidized by air and form allomelanins, nitrogen-free pigments similar to cutaneous melanins; by its high concentration in urine; and by the urine spraying behavior of red deer by which urine is spread through the ventral body area. Accordingly, the size of the dark ventral patch was positively correlated with the concentration of DOPEG in urine, which was in turn correlated with DOPEG absorbed in ventral hair. These findings represent catecholamine concentrations about one million higher than those previously reported for any hormone in an organism. This may have favored the evolution of the dark ventral patch of red deer by transferring information on the fighting capacity to rivals and mates. Physiological limits for hormone production in animals are thus considerably higher than previously thought. These results also unveil a novel mechanism of pigmentation based on the self-application of urine over the fur.Peer Reviewe

Physical Mechanisms Responsible for Electrical Conduction in Pt/GaN Schottky Diodes

The current-voltage (I-V) characteristics of Pt/(n.u.d)-GaN and Pt/Si-doped-GaN diodes Schottky are investigated. Based on these measurements, physical mechanisms responsible for electrical conduction have been suggested. The contribution of thermionic-emission current and various other current transport mechanisms were assumed when evaluating the Schottky barrier height. Thus the generation-recombination, tunneling and leakage currents caused by inhomogeneities and defects at metal-semiconductor interface were taken into account