scholarly journals Eumelanin and pheomelanin are predominant pigments in bumblebee (Apidae: Bombus) pubescence

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3300 ◽  
Author(s):  
Carlo Polidori ◽  
Alberto Jorge ◽  
Concepción Ornosa
Keyword(s):  
Chemical Nature ◽  
Apparent Effect ◽  
Vibrational States ◽  
Spectroscopy Analysis ◽  
Yellow Orange ◽  
Specific Variation ◽  
Single Precursor ◽  
Pubescence Color ◽  
Conclusive Data ◽  
Black Pigmentation

Background Bumblebees (Hymenoptera: Apidae: Bombus) are well known for their important inter- and intra-specific variation in hair (or pubescence) color patterns, but the chemical nature of the pigments associated with these patterns is not fully understood. For example, though melanization is believed to provide darker colors, it still unknown which types of melanin are responsible for each color, and no conclusive data are available for the lighter colors, including white. Methods By using dispersive Raman spectroscopy analysis on 12 species/subspecies of bumblebees from seven subgenera, we tested the hypothesis that eumelanin and pheomelanin, the two main melanin types occurring in animals, are largely responsible for bumblebee pubescence coloration. Results Eumelanin and pheomelanin occur in bumblebee pubescence. Black pigmentation is due to prevalent eumelanin, with visible signals of additional pheomelanin, while the yellow, orange, red and brown hairs clearly include pheomelanin. On the other hand, white hairs reward very weak Raman signals, suggesting that they are depigmented. Additional non-melanic pigments in yellow hair cannot be excluded but need other techniques to be detected. Raman spectra were more similar across similarly colored hairs, with no apparent effect of phylogeny and both melanin types appeared to be already used at the beginning of bumblebee radiation. Discussion We suggest that the two main melanin forms, at variable amounts and/or vibrational states, are sufficient in giving almost the whole color range of bumblebee pubescence, allowing these insects to use a single precursor instead of synthesizing a variety of chemically different pigments. This would agree with commonly seen color interchanges between body segments across Bombus species.

Carbon Nanostructures Produced by Liquid Phase Exfoliation of Graphite in the Presence of Small Organic Molecules

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Jesús I. Tapia ◽  
Mildred Quintana
Keyword(s):  
Liquid Phase ◽  
Small Molecules ◽  
Carbon Nanostructures ◽  
Organic Molecules ◽  
Chemical Nature ◽  
Spectroscopy Analysis ◽  
Small Organic Molecules ◽  
Transmission Electron ◽  
Secondary Reactions ◽  
Carbon Nanoscrolls

AbstractWe report on the formation of different carbon nanostructures by ultrasonication of graphite in DMF upon the addition of 3 different small molecules: ferrocene carboxylic acid, dimethylamino methyl-ferrocene, and benzyl aldehyde. Our results confirm that acoustic cavitation in organic solvents generates free radicals which enable or are involved in secondary reactions. During the ultrasonication process, the addition of small molecules induces the formation of different carbon nanostructures mainly depending on the chemical nature of the molecule, as observed by transmission electron microscopy (TEM). Raman spectroscopy analysis confirms that small molecules act as radical scavengers reducing the damage caused by cavitation to graphene sheets producing long nanoribbons, squared sheets, or carbon nanoscrolls. Importantly, this strategy allows the production of different carbon nanostructures in liquid-phase making them readily available for their chemical functionalization or for their incorporation into hybrids materials enabling the development of new advanced biological applications.

Fused Hybrid Linkers for Metal–Organic Frameworks-Derived Bifunctional Oxygen Electrocatalysts

2019 ◽  
Author(s):  
Kefeng Ping ◽  
Alan Braschinsky ◽  
Mahboob Alam ◽  
Rohit Bhadoria ◽  
Valdek Mikli ◽  
...  
Keyword(s):  
Chemical Nature ◽  
Metal Organic Framework ◽  
Fine Tuning ◽  
Nanostructured Carbon ◽  
Organic Additives ◽  
Carbon Supports ◽  
Metal Organic ◽  
Single Precursor ◽  
Organometallic Precursors ◽  
Organic Linker

<div> <div> <div> <p>Preparation of electrocatalysts often relies on the use of multiple starting materials – inorganic salts or organometallic precursors, nanostructured carbon supports, organic additives, dopants and carbonization under modifying atmospheres (e.g. NH<sub>3 </sub>or H<sub>2</sub>) – with the examples of electrocatalysts arising from a single precursor being much less common. Herein, we have surveyed a series of heterobivalent scaffolds to identify an iron/benzimidazole-based metal– organic framework as a uniform starting material. By merging the catechol and imidazole units together, we get direct entry into a highly efficient bifunctional oxygen electrocatalyst, which alleviates the need for additional dopants and modifying conditions (ORR: <i>E</i><sub>on</sub> = 1.01 V, <i>E</i><sub>1/2</sub> = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm<sup>–2</sup> in 0.1 M KOH; ∆<i>E</i> = 0.73 V). We demonstrate that by fine-tuning the chemical nature of an organic linker, one is able modulate the electrochemical properties of a single precursor-derived electrocatalyst material. </p> </div> </div> </div>

Fused Hybrid Linkers for Metal–Organic Frameworks-Derived Bifunctional Oxygen Electrocatalysts

2019 ◽  
Author(s):  
Kefeng Ping ◽  
Alan Braschinsky ◽  
Mahboob Alam ◽  
Rohit Bhadoria ◽  
Valdek Mikli ◽  
...  
Keyword(s):  
Chemical Nature ◽  
Metal Organic Framework ◽  
Fine Tuning ◽  
Nanostructured Carbon ◽  
Organic Additives ◽  
Carbon Supports ◽  
Metal Organic ◽  
Single Precursor ◽  
Organometallic Precursors ◽  
Organic Linker

<div> <div> <div> <p>Preparation of electrocatalysts often relies on the use of multiple starting materials – inorganic salts or organometallic precursors, nanostructured carbon supports, organic additives, dopants and carbonization under modifying atmospheres (e.g. NH<sub>3 </sub>or H<sub>2</sub>) – with the examples of electrocatalysts arising from a single precursor being much less common. Herein, we have surveyed a series of heterobivalent scaffolds to identify an iron/benzimidazole-based metal– organic framework as a uniform starting material. By merging the catechol and imidazole units together, we get direct entry into a highly efficient bifunctional oxygen electrocatalyst, which alleviates the need for additional dopants and modifying conditions (ORR: <i>E</i><sub>on</sub> = 1.01 V, <i>E</i><sub>1/2</sub> = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm<sup>–2</sup> in 0.1 M KOH; ∆<i>E</i> = 0.73 V). We demonstrate that by fine-tuning the chemical nature of an organic linker, one is able modulate the electrochemical properties of a single precursor-derived electrocatalyst material. </p> </div> </div> </div>

Porous Silicon Luminescence Study by Imaging Methods: Relationship to Pore Dimensions

1994 ◽  
Vol 332 ◽  
Author(s):  
Anna Kontkiewicz ◽  
Andrzej M. Kontkiewicz ◽  
Sidhartha Sen ◽  
Marek Wesolowski ◽  
Jacek Lagowski ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Porous Silicon ◽  
Size Effects ◽  
Chemical Nature ◽  
Surface Photovoltage ◽  
Quantum Size Effects ◽  
Optical Absorption Edge ◽  
Spectroscopy Analysis ◽  
Quantum Size ◽  
Atomic Force

ABSTRACTIn a photoluminescence and surface photovoltage study of porous silicon films with crystallite dimensions assessed with the Atomic Force Microscope, we have found cases when the blue shifts of the luminescence spectrum and the optical absorption edge take place upon increasing crystallite dimensions, which is contrary to quantum size effects. Fourier transform infrared spectroscopy analysis of these samples shows significant differences in hydrogen and oxygen bonding, which imply that the origin of the luminescence is of chemical nature. Our results show that porous silicon luminescence is not a consequence of one mechanism, but rather results from several mechanisms with contributions depending on the chemistry and structure of porous silicon.

Fused Hybrid Linkers for Metal–Organic Frameworks-Derived Bifunctional Oxygen Electrocatalysts

2019 ◽  
Author(s):  
Kefeng Ping ◽  
Alan Braschinsky ◽  
Mahboob Alam ◽  
Rohit Bhadoria ◽  
Valdek Mikli ◽  
...  
Keyword(s):  
Chemical Nature ◽  
Metal Organic Framework ◽  
Fine Tuning ◽  
Nanostructured Carbon ◽  
Organic Additives ◽  
Carbon Supports ◽  
Metal Organic ◽  
Single Precursor ◽  
Organometallic Precursors ◽  
Organic Linker

<div> <div> <div> <p>Preparation of electrocatalysts often relies on the use of multiple starting materials – inorganic salts or organometallic precursors, nanostructured carbon supports, organic additives, dopants and carbonization under modifying atmospheres (e.g. NH<sub>3 </sub>or H<sub>2</sub>) – with the examples of electrocatalysts arising from a single precursor being much less common. Herein, we have surveyed a series of heterobivalent scaffolds to identify an iron/benzimidazole-based metal– organic framework as a uniform starting material. By merging the catechol and imidazole units together, we get direct entry into a highly efficient bifunctional oxygen electrocatalyst, which alleviates the need for additional dopants and modifying conditions (ORR: <i>E</i><sub>on</sub> = 1.01 V, <i>E</i><sub>1/2</sub> = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm<sup>–2</sup> in 0.1 M KOH; ∆<i>E</i> = 0.73 V). We demonstrate that by fine-tuning the chemical nature of an organic linker, one is able modulate the electrochemical properties of a single precursor-derived electrocatalyst material. </p> </div> </div> </div>

Autostoichiometric Mocvd Of Multicomponent Thin Films LiTaO3, LiNbO3 and SrxBa1-xNbO6

1999 ◽  
Vol 597 ◽  
Author(s):  
R. Zhang ◽  
R. Xu
Keyword(s):  
Thin Films ◽  
Single Phase ◽  
Evaluation Method ◽  
Chemical Nature ◽  
Decomposition Analysis ◽  
Deposition Process ◽  
Heterometallic Alkoxides ◽  
Evaporation Characteristic ◽  
Single Precursor ◽  
Heterometallic Alkoxide

AbstractA novel stoichiometric vapor deposition process, Autostoichiometric MOCVD, was developed in this study to prepare stoichiometric thin films. Heterometallic alkoxides were used as single precursor for two different metal components in Autostoichiometric MOCVD. The molecular ratios of the metals were conserved through the precursor evaporation and the deposition reactions based on the chemical nature of precursors and the deposition reaction mechanisms. A non-stoichiometric factor K was defined to study the evaporation process of precursors. A precursor evaluation method using the K factor and the thermal decomposition analysis was introduced to quantitatively analyze the stoichiometric evaporation characteristic of a heterometallic alkoxide precursor. Single phase LiTaO3, LiNbO3, SrNb2O6 and BaNb2O6 films were successfully obtained using precursor LiTa(n-OBut)6 or LiTa(i-OBut)6, LiNb(n-OBut)6, SrNb2(n-OBut)12 and BaNb2(n-OBut)12, respectively. Solid solution Sr1-x.BaxNb2O6(SBN) films were also successfully obtained by a two-step Autostoichiometric MOCVD.

Release of Neurosecretion in the Crayfish Sinus Gland

1968 ◽  
Vol 26 ◽  
pp. 150-151
Author(s):  
Richard R. Shivers
Keyword(s):  
Chemical Nature ◽  
Storage Site ◽  
Neurosecretory Granules ◽  
Sinus Gland ◽  
Diameter Class ◽  
Dense Membrane ◽  
Neurohemal Organ ◽  
Dense Vesicles

The sinus gland is a neurohemal organ located in the crayfish eyestalk and represents a storage site for neurohormones prior to their release into the circulation. The sinus gland contains 3 classes of dense, membrane-limited granules: 1) granules measuring less than 1000 Å in diameter, 2) granules measuring 1100-1400 Å in diameter, and 3) granules measuring 1500-2000 Å in diameter. Class 3 granules are the most electron-dense of the granules found in the sinus gland, while class 2 granules are the most abundant. Generally, all granules appear to undergo similar changes during release.Release of neurosecretory granules may be initiated by a preliminary fragmentation of the “parent granule” into smaller, less dense vesicles which measure about 350 Å in diameter (V, Figs. 1-3). A decrease in density of the granules prior to their fragmentation has been observed and may reflect a change in the chemical nature of the granule contents.

Freeze-fracture cytochemistry: A goal set by Russell Steere in 1957

1993 ◽  
Vol 51 ◽  
pp. 60-61
Author(s):  
Nicholas J Severs
Keyword(s):  
Chemical Nature ◽  
Biological Systems ◽  
Freeze Fracture ◽  
Structural Components ◽  
Major Goal ◽  
Membrane Biology ◽  
Routine Application ◽  
The Future ◽  
Freeze Etching

In his pioneering demonstration of the potential of freeze-etching in biological systems, Russell Steere assessed the future promise and limitations of the technique with remarkable foresight. Item 2 in his list of inherent difficulties as they then stood stated “The chemical nature of the objects seen in the replica cannot be determined”. This defined a major goal for practitioners of freeze-fracture which, for more than a decade, seemed unattainable. It was not until the introduction of the label-fracture-etch technique in the early 1970s that the mould was broken, and not until the following decade that the full scope of modern freeze-fracture cytochemistry took shape. The culmination of these developments in the 1990s now equips the researcher with a set of effective techniques for routine application in cell and membrane biology.Freeze-fracture cytochemical techniques are all designed to provide information on the chemical nature of structural components revealed by freeze-fracture, but differ in how this is achieved, in precisely what type of information is obtained, and in which types of specimen can be studied.

Cell parameters refinements showing an influence of the chemical nature of the grain surface on the crystalline characteristics of fine grained powders

1998 ◽  
Vol 08 (PR5) ◽  
pp. Pr5-85-Pr5-89
Author(s):  
P. Sarrazin ◽  
F. Bernard ◽  
G. Calvarin ◽  
J. C. Niepce ◽  
B. Thierry
Keyword(s):  
Chemical Nature ◽  
Cell Parameters ◽  
Fine Grained ◽  
Grain Surface
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