ChemTexts

Vincenzo Palleschi

Laser-induced breakdown spectroscopy: principles of the technique and future trends

激光诱导击穿光谱：技术原理与未来趋势

Abstract Nootkatone is one of the most valuable citrus flavors. Originally isolated from the heartwood of the Nootka cypress ( Callitropsis nootkatensis ), it was probably the identification of nootkatone as a minor component of grapefruit oil that catapulted this sesquiterpene into the focus of flavor research and made it a highly sought-after citrus aroma in recent decades. The odors of ( +)-nootkatone and (−)-nootkatone are perceptible in the air at threshold concentrations of 30 ppm and 66,000 ppm of saturated vapor, respectively. While ( +)-nootkatone embodies a strong grapefruit scent and has a bitter taste, (−)-nootkatone has a faint woody vetiver note and is virtually tasteless. In 2020, nootkatone was registered by the US Environmental Protection Agency as an insect repellent and natural insecticide that may repel and kill mosquitoes, fleas, ticks, mites, lice, and termites. Moreover, numerous pharmacological activities of nootkatone have been thoroughly investigated. As expected, a wealth of synthetic approaches, which are essentially based on the oxidation of valencene and on total syntheses, have been published in the last 60 years since its discovery. However, in addition to extraction from natural sources (e.g., grapefruit peel), the enzymatic oxidation of valencene and fermentative processes are the preferred production technologies today. The market is expected to grow considerably over the next 10 years, not least owing to the wide range of potential applications in the pharmaceutical, personal, and home care sector. How the reader may benefit : learn more about the total synthesis of natural products, allylic oxidation, and Robinson annulation, gain deeper insights into the biosynthesis of sesquiterpenes and finally discover how enantiopure compounds, such as ( +)-nootkatone, are produced at an industrial scale. Graphical Abstract

Raghavendra Ramachanderan

Bernd Schaefer

(+)-Nootkatone, the flavor of grapefruit

(+)-诺卡酮，葡萄柚的风味

Abstract Tyrosinases (TYRs) are a family of copper-containing metalloenzymes that are present in all domains of life. TYRs catalyze the reactions that start the biosynthesis of melanin, the main pigment of the animal kingdom, and are also involved in the formation of the bright colors seen on the caps of mushrooms and in the petals of flowers. TYRs catalyze the ortho -hydroxylation and oxidation of phenols and the oxidation of catechols to the respective o -quinones. They only need molecular oxygen to do that, and the products of TYRs— o -quinones—are highly reactive and will usually react with the next available nucleophile. This reactivity can be harnessed for pharmaceutical applications as well as in environmental and food biotechnology. The majority of both basic and applied research on TYRs utilizes “mushroom tyrosinase”, a crude enzyme preparation derived from button mushroom ( Agaricus bisporus ) fruiting bodies. Access to pure TYR preparations comes almost exclusively from the production of recombinant TYRs as the purification of these enzymes from the natural source is usually very laborious and plagued by low yields. In this text an introduction into the biochemistry of the enzyme TYR will be given, followed by an overview of available structural data of TYRs, the current model for the catalytic mechanism, a survey of reports on the recombinant production of this important metalloenzyme family, and a review of the applications of TYRs for the synthesis of catechols, as biosensors, in bioremediation, for the cross-linking of proteins and medical hydrogels as well as for melanoma treatment. Graphical Abstract

Matthias Pretzler

Annette Rompel

Tyrosinases: a family of copper-containing metalloenzymes

酪氨酸酶：一种含铜金属酶家族

Alejandro Pérez Paz

Exact solutions of reversible dimerization and trimerization kinetics

可逆二聚和三聚动力学的精确解

Ingrid Rodríguez-Hernández

Berenice Miranda-Alcántara

German Orozco

Introduction to electrochemical science using Legendre transforms

使用勒让德变换的电化学科学导论

Todd P. Silverstein

Le Chatelier’s principle for constant pressure reactions: a mnemonic diagram to judge potential pitfalls

常压反应的勒夏特列原理：判断潜在陷阱的助记图

Abbreviation	ChemTexts
Journal Impact	2.95
Quartiles(Global)	CHEMISTRY, MULTIDISCIPLINARY(Q2)

ISSN	2199-3793
h-index	21

Publication Information	Publisher: Springer International Publishing AG，Publishing cycle: ，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 2015，Proportion of original research papers: 100.00%，Self Citation Rate:3.40%， Gold OA Rate: 38.89%

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Laser-induced breakdown spectroscopy: principles of the technique and future trends

(+)-Nootkatone, the flavor of grapefruit

Tyrosinases: a family of copper-containing metalloenzymes

Exact solutions of reversible dimerization and trimerization kinetics

Introduction to electrochemical science using Legendre transforms

Tyrosinases: a family of copper-containing metalloenzymes

(+)-Nootkatone, the flavor of grapefruit

Introduction to electrochemical science using Legendre transforms

Exact solutions of reversible dimerization and trimerization kinetics

Le Chatelier’s principle for constant pressure reactions: a mnemonic diagram to judge potential pitfalls