Synthesis and Characterization of Quantum Dot Nanoparticles Bound to the Plant Volatile Precursor of Hydroxy-apo-10′-carotenal

Bioorthogonal chemical reporters for profiling retinoic acid-modified and retinoic acid-interacting proteins

Vitamin A and its primary active derivative, all-trans retinoic acid (RA), are endogenous signaling molecules essential for numerous biological processes, including cell proliferation, differentiation, and immune modulation. Owing to its differentiation-inducing effect, RA was the first differentiating agent approved for the clinical treatment of acute myeloid leukemia. While the classical mechanisms of RA signaling involve nuclear receptors, such as retinoic acid receptors (RARs), emerging evidence suggests that RA also engages in non-covalent and covalent interactions with a broader range of proteins. However, tools for thoroughly characterizing these interactions have been lacking, and a comprehensive understanding of the landscape of RA-modified and RA-interacting proteins remains limited. Here, we report the development of two RA-based chemical reporters, RA-yne and RA-diazyne, to profile RA-modified and RA-interacting proteins, respectively, in live cells. RA-yne features a clickable alkyne group for metabolic labeling of RA-modified proteins, while RA-diazyne incorporates a photoactivatable diazirine and an alkyne handle for crosslinking and capturing RA-interacting proteins. Using quantitative proteomics, we demonstrate the high-throughput identification of these proteins, revealing that non-covalent interactions are more prevalent than covalent modifications. Our global profiling also uncovers a large number of RA-interacting proteins mainly enriched in pathways related to mitochondrial processes, ER homeostasis, and lipid metabolism. Overall, this work introduces new RA-derived chemical reporters, expands the resource for studying RA biology, and enhances our understanding of RA-associated pathways in health and disease.

Oxidation of Terpenoids to Achieve High-Value Flavor and Fragrances—Questioning Microalgae Oxidative Capabilities in the Biotransformation of the Sesquiterpene Valencene and of Selected Natural Apocarotenoids

Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.

Fungi-Mediated Biotransformation of the Isomeric Forms of the Apocarotenoids Ionone, Damascone and Theaspirane

In this work, we describe a study on the biotransformation of seven natural occurring apocarotenoids by means of eleven selected fungal species. The substrates, namely ionone (α-, β- and γ-isomers), 3,4-dehydroionone, damascone (α- and β-isomers) and theaspirane are relevant flavour and fragrances components. We found that most of the investigated biotransformation reactions afforded oxidized products such as hydroxy- keto- or epoxy-derivatives. On the contrary, the reduction of the keto groups or the reduction of the double bond functional groups were observed only for few substrates, where the reduced products are however formed in minor amount. When starting apocarotenoids are isomers of the same chemical compound (e.g., ionone isomers) their biotransformation can give products very different from each other, depending both on the starting substrate and on the fungal species used. Since the majority of the starting apocarotenoids are often available in natural form and the described products are natural compounds, identified in flavours or fragrances, our biotransformation procedures can be regarded as prospective processes for the preparation of high value olfactory active compounds.

In Vivo Delivery of Nanoparticles into Plant Leaves

Plant nanobiotechnology is an interdisciplinary field at the interface of nanotechnology and plant biology that aims to utilize nanomaterials as tools to study, augment or impart novel plant functions. The delivery of nanoparticles to plants in vivo is a key initial step to investigate plant nanoparticle interactions and the impact of nanoparticles on plant function. Quantum dots are smaller than plant cell wall pores, have versatile surface chemistry, bright fluorescence and do not photobleach, making them ideal for the study of nanoparticle uptake, transport, and distribution in plants by widely available confocal microscopy tools. Herein, we describe three different methods for quantum dot delivery into leaves of living plants: leaf lamina infiltration, whole shoot vacuum infiltration, and root to leaf translocation. These methods can be potentially extended to other nanoparticles, including nanosensors and drug delivery nanoparticles. © 2017 by John Wiley & Sons, Inc.

Synthesis and reactivity of a 4His enzyme model complex

A new iron(II) complex has been prepared and characterized. [Fe(TrIm)4(OTf)2] (1, TrIm = 1-Tritylimidazole). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in triclinic space group P1̄, with a = 13.342(7) Å, b = 13.5131(7) Å and c = 13.7025(7) Å. The iron center resides in distorted octahedral geometry coordinated to four equatorial imidazole groups and two axial triflate oxygens groups. The complex is high spin between 20 K and 300 K as indicated by variable field variable temperature magnetic measurements. A fit of the magnetic data yielded g = 2.24 and D = -0.80 cm-1. A large HOMO-LUMO gap energy (3.89 eV) exists for 1 indicating high stability. Addition of H2O2 or t BuOOH to 1 results in formation of an oxygenated intermediate which upon decomposition results in oxidation of the trityl substituent on the imidazole ligand.

Selective oxidation of carotenoid-derived aroma compounds by CYP260B1 and CYP267B1 from Sorangium cellulosum So ce56

Due to their bioactive properties as well as their application as precursors in chemical synthesis, hydroxylated isoprenoids and norisoprenoids are very valuable compounds. The efficient hydroxylation of such compounds remains a challenge in organic chemistry caused by the formation of a variety of side products and lack of overall regio- and stereoselectivity. In contrast, cytochromes P450 are known for their selective oxidation under mild conditions. Here, we demonstrate for the first time the ability of myxobacterial CYP260B1 and CYP267B1 from Sorangium cellulosum So ce56 to oxidize such carotenoid-derived aroma compounds. A focused library of 14 substrates such as ionones, damascones, as well as some of their isomers and derivatives was screened in vitro. Both P450s were capable of an efficient oxidation of all tested compounds. CYP260B1-dependent conversions mainly formed multiple products, whereas conversions by CYP267B1 resulted predominantly in a single product. To identify the main products by NMR spectroscopy, an Escherichia coli-based whole-cell system was used. CYP267B1 showed a hydroxylase activity towards the formation of allylic alcohols. Likewise, CYP260B1 performed the allylic hydroxylation of β-damascone [(E)-1-(2,6,6-trimethylcyclohex-1-enyl)but-2-en-1-one] and δ-damascone [(E)-1-(2,6,6-trimethylcyclohex-3-enyl)but-2-en-1-one]. Moreover, CYP260B1 showed an epoxidase activity towards β-ionone [(E)-4-(2,6,6-trimethylcyclohex-1-enyl)but-3-en-2-one] as well as the methyl-substituted α-ionone derivatives raldeine [(E)-1-(2,6,6-trimethylcyclohex-2-enyl)pent-1-en-3-one] and isoraldeine [(E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-enyl)but-3-en-2-one]. In addition, to known products, also novel products such as 2-OH-δ-damascone [(E)-1-(5-hydroxy-2,6,6-trimethylcyclohex-3-enyl)but-2-en-1-one], 3-OH-allyl-α-ionone [(E)-1-(4-hydroxy-2,6,6-trimethylcyclohex-2-enyl)hepta-1,6-dien-3-one], and 4-OH-allyl-β-ionone [(E)-1-(3-hydroxy-2,6,6-trimethylcyclohex-1-enyl)hepta-1,6-dien-3-one] were identified during our studies.