Monitoring Photosynthetic Activity in Microalgal Cells by Raman Spectroscopy with Deuterium Oxide as a Tracking Probe

Microalgae offer great potential for the production of biofuel, but high photosynthetic activity is demanded for the practical realisation of microalgal biofuels. To this end, it is essential to evaluate the photosynthetic activity of single microalgal cells in a heterogeneous population. In this study, we present a method to monitor the photosynthetic activity of microalgae (in particular Euglena gracilis, a microalgal species of unicellular, photosynthetic, flagellate protists as our model organism) at single-cell resolution by Raman spectroscopy with deuterium from deuterium oxide (D₂O) as a tracking probe. Specifically, we replaced H₂O in culture media with D₂O up to a concentration of 20 % without disturbing the growth rate of E. gracilis cells and evaluated C−D bond formation as a consequence of photosynthetic reactions by Raman spectroscopy. We used the probe to monitor the kinetics of the C−D bond formation in E. gracilis cells by incubating them in D₂O media under light irradiation. Furthermore, we demonstrated Raman microscopy imaging of each single E. gracilis cell to discriminate deuterated cells from normal cells. Our results hold great promise for Raman-based screening of E. gracilis and potentially other microalgae with high photosynthetic activity by using D₂O as a tracking probe.     

Assembly of Fully Substituted 2H-Indazoles Catalyzed by Cu2O Rhombic Dodecahedra and Evaluation of Anticancer Activity

Simultaneous C−N, and N−N bond-forming methods for one-pot transformations are highly challenging in synthetic organic chemistry. In this study, the Cu₂O rhombic dodecahedra-catalyzed synthesis of 2H-indazoles is demonstrated with good to excellent yields from readily available chemicals. This one-pot procedure involves Cu₂O nanoparticle-catalyzed consecutive C−N, and N−N bond formation followed by cyclization to yield 2H-indazoles with broad substrate scope and high functional group tolerance. Various cell-based bioassay studies demonstrated that 2H-indazoles inhibit the growth of cancer cells, typically through induction of apoptosis in a dose-dependent manner. Moreover, 2H-indazoles tested in the MDA-MB-468 cell line were capable of inhibiting cancer cell migration and invasion. Thus, it is shown that 2H-indazoles have potent in vitro anticancer activity that warrant further investigation of this compound class.     

Energetic Materials Designing Bench (EMDB), Version 1.0

EMDB_1 is a new professional package in the area of EMs, which calculates more than thirty physicochemical properties and detonation parameters for different pure explosives or energetic formulations (for C−H−N−O−F−Cl−Al−Br−I−S compounds). Here we present the results of performance (VoD) calculations obtained using the EMDB, EXPLO5 and CHEETAH programs, and compare these values with the experimentally determined values. We also calculated the impact and friction sensitivities using the EMDB code, and compared the values obtained with measured values.     

Coordination Dynamics of Iron is a Key Player in the Catalysis of Non-heme Enzymes

Mononuclear nonheme iron enzymes catalyze a large variety of oxidative transformations responsible for various biosynthesis and metabolism processes. Unlike their P450 counterparts, non-heme enzymes generally possess flexible and variable coordination architecture, which can endow rich reactivity for non-heme enzymes. This Concept highlights that the coordination dynamics of iron can be a key player in controlling the activity and selectivity of non-heme enzymes. In ergothioneine synthase EgtB, the coordination switch of the sulfoxide radical species enables the efficient and selective C−S coupling reaction. In iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenases, the conformational flip of ferryl-oxo intermediate can be extensively involved in selective oxidation reactions. Especially, the five-coordinate ferryl-oxo species may allow the substrate coordination via O or N atom, which may facilitate the C−O or C−N coupling reactions via stabilizing the transition states and inhibiting the unwanted hydroxylation reactions.     

In situ fourier‐transform infrared spectra analysis of hydrogen bond in polypropylene/chlorinated polypropylene/polyaniline composite

The previous studies suggest that hydrogen bond between chlorinated polypropylene (CPP) and polyaniline (PANI) plays a prominent role in the decision of polypropylene/CPP/PANI composites' electric property. In situ Fourier‐transform infrared spectra were employed to detect and identify the relationship between the hydrogen bond and the temperature. Two kinds of hydrogen bond were carefully studied in the nitrogen–hydrogen bond (N? H) stretching, sulfur–oxygen double bond (S?O) stretching, and carbon–chlorine bond (C? Cl) stretching regions, using an iterative least‐squares computer program to obtain the best fit of spectra. The ratio of absorptivity coefficients and the mole fraction of the “free” and two kinds of H‐bonded N? H were calculated. There exists an apparent turning point in the curves of the relationship between the fraction of two kinds of H‐bonded N? H and temperature. This phenomenon also exists in the S?O stretching region, and the turning point is at about 60°C. The mole fraction of H‐bonded C? Cl decreases, and that of “free” C? Cl increases with increasing temperature. The enthalpy gap between the H‐bonded N? H…O?S and the H‐bonded N? H…Cl?C dissociation was also obtained as 23.2 KJ/mol. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Small Ring Compounds and N-oxides: Cycloadditions and Related Processes

The review discusses the possibilities for reactions of small ring compounds (cyclopropanes, cyclobutanes, and their heteroanalogs) with various N-oxides (nitrones, nitronates, nitrile oxides, etc.). Two major paths include: formal cycloadditions of small cycles with N-oxide possessing dipoles, and [3+2] cycloadditions of small cyclic alkenes with N-oxides, followed by N−O bond cleavage-assisted rearrangement/ring opening.     

Mechanistic Insights on the Formation of High-Valent MnIII/IV=O Species Using Oxygen as Oxidant: A Theoretical Perspective

High-valent metal−oxo species are of great interest as they serve as a robust catalyst for various organic transformations, and at the same time, they offer significant insight into the reactivity of various metalloenzymes. Formation of Mn−Oxo species is of great interest as they are involved in the Oxygen Evolving Complex of Photosystem II, and various bio-mimic models were synthesized to understand its reactivity. In this context, using urea decorated amine ligands, Borovik et al. have reported the facile formation of Mn^III=O and Mn^IV=O species from [Mn^IIH₂buea]²⁻ (here H2buea=tris[(N′-tert-butylureayl)-N-ethyl]amine) precursor complex using oxygen as the oxidant. While reactivity of these species is thoroughly studied, mechanism of formation of such species is scarcely explored. In this work, we have attempted to establish the formation of these species from the Mn^II precursor using the experimental conditions. Our calculations reveal the following fundamental steps in the formation of such species: i) O₂ activation by Mn^II lead to formation of Mn^II−superoxide species wherein the oxidation state of the Mn^II found to be intact upon O₂ binding facilitated by the deprotonated nitrogen atom present in the cavity (ii) in the second step, superoxo species is converted to Mn^II−hydroperoxo species, [Mn^IIH₂buea(OOH)]²⁻ using dimethylacetamide solvent as source for HAT reaction (iii) presence of water molecule found to aid the O−O bond cleavage in [Mn^IIH₂buea(OOH)]²⁻ species leading to the formation of the putative Mn^III=O species, [Mn^IIIH₃buea(O)]²⁻ (iv) one-electron oxidation of Mn^III=O, leads to the formation of [Mn^IVH₃buea(O)]⁻ species and this step is endothermic and need some external oxidants for its formation. While various spin-states and their roles are explored, our calculations reveal that the Mn atom prefers to be in the high-spin state across the potential energy surface studied. However, the nature of the formation is strongly correlated to the spin state arising from the radical nature present in the O₂ moiety and also in the deprotonated nitrogen atom. This offers a unique multistate reactivity channel for the formation these species easing various kinetic barriers across the potential energy surface. Further, we have also computed the spectral parameters for the experimentally observed species, which are in agreement with the reported data offering confidence on the mechanism established. To this end, our study unveils a facile formation of high-valent Mn−Oxo species using O₂ as oxidant and role of water molecules in the formation of such species, and these mechanistic insights are likely to have implications beyond the example studied here.     

Iron-Catalyzed C−C Bond Formation via Chelation-Assisted C−H Activation

This review provides a brief overview of iron-catalyzed C−C bond forming reactions via heteroatom-assisted C−H bond activation, which have been extensively developed in the last decade. Three major types of reactions are discussed, namely, (1) C−H activation/C−C coupling using organometallic reagents under oxidative conditions, (2) C−H activation/C−C coupling using organic electrophiles under redox-neutral conditions, and (3) C−H activation/C−C coupling using unsaturated hydrocarbons under redox-neutral or oxidative conditions.     

2‐Arylacetamides as Versatile Precursors for 3‐Aminoisocoumarin and Homophthalimide Derivatives: Palladium‐Catalyzed Cascade Double Carbonylation Reactions

The synthesis of biologically relevant homophthalimide and 3‐aminoisocoumarin nuclei via palladium‐catalyzed carbonylation of 2‐(2‐iodoaryl)acetamides has been developed. The degree of N‐substitution on the starting amide substrate dictates whether C−N or C−O coupling takes place in the final step of the catalytic cycle giving rise to each type of heterocycle. The introduction of a second C−halogen bond in the starting acetamides allows a catalytic cascade double carbonylation involving a C−H activation step to give fused heterocyclic structures.

     

Synthesis and Liver Microsomal Metabolic Stability Studies of a Fluorine-Substituted δ-Tocotrienol Derivative

A fluoro-substituted δ-tocotrienol derivative, DT3-F2, was synthesized. This compound was designed to stabilize the metabolically labile terminal methyl groups of δ-tocotrienol by replacing one C−H bond on each of the two methyl groups with a C−F bond. However, in vitro metabolic stability studies using mouse liver microsomes revealed an unexpected rapid enzymatic C−F bond hydrolysis of DT3-F2. To the best of our knowledge, this is the first report of an unusual metabolic hydrolysis of allylic C−F bonds.     

A molecular dynamics study of N–A–S–H gel with various Si/Al ratios

In this paper, the atomic structures of sodium aluminosilicate hydrate (N–A–S–H) gels with different Si/Al ratios are studied by molecular dynamics simulation. An N–A–S–H gel model was obtained from the polymerization of Si(OH)₄ and Al(OH)₃ monomers with the use of a reactive force field (ReaxFF). The simulated atomic structural features, such as the bond length, bond angle, and simulated X-ray diffraction pattern of the gel structure are in good accordance with the experimental results in the literature. Si–O–Al is found to be preferred over Si–O–Si in the N–A–S–H gel structure according to the amount of T–O–T bond angles and distribution of Si⁴(mAl). Pentacoordinate Al is identified in all simulated N–A–S–H models. It provides strong support to current knowledge that pentacoordinate Al in geopolymer does not only come from raw material. Furthermore, the structural analysis results also show that N–A–S–H gel with lower Si/Al ratios has a more cross-linked and compacted structure.     

Copper(I)-Dioxygen Adducts and Copper Enzyme Mechanisms

Primary copper(I)-dioxygen (O₂) adducts, cupric-superoxide complexes, have been proposed intermediates in copper-containing dioxygen-activating monooxygenase and oxidase enzymes. Here, mechanisms of C−H activation by reactive copper-(di)oxygen intermediates are discussed, with an emphasis on cupric-superoxide species. Over the past 25 years, many synthetically derived cupric-superoxide model complexes have been reported. Due to the thermal instability of these intermediates, early studies focused on increasing their stability and obtaining physical characterization. More recently, in an effort to gain insight into the possible substrate oxidation step in some copper monooxygenases, several cupric-superoxide complexes have been used as surrogates to probe substrate scope and reaction mechanisms. These cupric superoxides are capable of oxidizing substrates containing weak O−H and C−H bonds. Mechanistic studies for some enzymes and model systems have supported an initial hydrogen-atom abstraction via the cupric-superoxide complex as the first step of substrate oxidation.     

Photochemical C−H Activation: An Early Story

An early investigation in the author‘s laboratory into photochemical C−H bond activation and functionalization is recounted. Specifically, d⁸ Ir(I) and Rh(I) carbonyl phosphine complexes were found to promote benzene C−H bond activtion and functionalization to give benzaldehyde upon near-UV irradiation. The carbonylation of benzene is thermodynamically unfavorable resulting in only low yields of benzaldehyde. The photochemical process was suggested as ligand dissociation to yield a 14 e⁻ Ir(I) or Rh(I) intermediate capable of benzene C−H oxidative additions. The research set the stage for subsequent photochemical C−H activation and functionalization studies by others in the late 1980’s.     

Indium‐Catalyzed Formal N‐Arylation and N‐Alkylation of Pyrroles with Amines

Under indium Lewis acid catalysis, a nitrogen atom of N‐unsubstituted pyrroles was replaced with a nitrogen atom of primary amines, thereby producing N‐aryl‐ and N‐alkylpyrroles. This system formally introducing such carbon frameworks to the pyrrole nitrogen atom shows unique selectivity: only the H−N(pyrrolyl) unit undergoes the N‐arylation and N‐alkylation even in the coexistence of a similar H−N(indolyl) part; and an aryl–halogen bond remains intact. These are clearly different from the typical method depending on the C−N(pyrrolyl) bond‐forming reaction with organic halides as substrates. From a viewpoint of pyrrole N‐protection–deprotection chemistry, worth noting is that a methyl group on the pyrrole nitrogen atom can be removed, albeit in a formal way.

     

Charge Distribution in 3′-Deoxythymidine-Fullerene: Mass Spectrometry,Laser Excitation,and Computational Studies

Electrospray ionization of the donor–spacer–acceptor model system 3′-imino[60]fulleryl-3′-deoxythymidine molecule (FdT) produces deprotonated negatively charged species (dFdT). In this paper, we investigate where the negative charge is localized and whether its location can be manipulated. The fragmentation of dFdT is studied experimentally by mass spectrometry using both collisional and photoactivation. Besides fragmentation, photoexcitation of anions stored in an ion trap leads to electron photodetachment. The competition between the two channels is studied as a function of the excitation wavelength. Starting from the neutral parents, two families of dFdT molecules are computationally identified. Deprotonation takes place on the 3′-deoxythymidine (dT) subunit, either on the thymine at N3 or on the deoxyribose residue at O5′. Deprotonation in N3 leads to negatively charged molecules with an extended geometry and the excess charge largely localized on the dT The O5′-deprotonation leads to lower-energy folded conformers stabilized by an additional bond (C–O or C–H) with the nearby C₆₀–N acceptor part, and the negative charge is mostly localized on the fullerene. The calculated electron detachment energies are higher for the extended N3dFdT conformers than for the O5′dFdT ones. Multiphoton photodetachment experiments at 1064 nm indicate the negative charge to be on the C₆₀ unit. No indication for a photoinduced charge transfer was found. In MS beside the C₆₀ anion a C₆₀NH₂– fragment is observed, which implies a double intramolecular H transfer. The computed energy of the corresponding dFdT, stabilized by two H–C₆₀ bonds, is intermediate between N3 and O5′ deprotonated molecules.     

HA和HNAPO萃取锌的密度泛函分析

为从微观层面分析从锌氨溶液中萃取Zn(II)的反应机理,采用密度泛函(DFT) B3LYP/6-31G+(d, p)理论对萃取剂1-苯基-1,3癸二酮(Mextral54-100,HA)和2-羟基-5-壬酰基苯甲酮肟(Lix84I,HNAPO)及Zn(II)萃合物的几何结构、红外光谱、原子轨道贡献率和电荷分布等进行研究。结果表明,在HA与锌形成萃合物的过程中,HA烯醇式上的O和C原子、HNAPO肟基上的C和N原子及苯酚上的O原子对分子轨道的贡献率最高;HA上的C=C双键的伸缩振动峰在萃取反应后发生红移,HNAPO肟基上的C=N双键的伸缩振动峰强度发生改变,酚羟基的摇摆振动峰消失,表明烯醇式、肟基和酚羟基为萃取反应的活性中心,键长和键角均发生了改变;Zn(II)取代烯醇式上的氢与氧原子形成配位键,C=O双键在形成萃合物后键长增大。HNAPO与锌形成萃合物的过程中,Zn(II)取代酚羟基上的氢与氧和氮原子形成配位键,且苯环和锌离子处于一个平面上;萃取剂HA的分子轨道差值和电负性均低于HNAPO,化学势高于HNAPO,理论预测HA萃取锌的反应活性大于HNAPO,与实验结果吻合。     

IGMH-based research on the intramolecular weak interaction of TKX-50

To further comprehensively study the intramolecular weak interaction of the gaseous TKX-50 molecule, the two conformations of the TKX-50 molecule were analyzed via the Independent Gradient Model based on the Hirshfeld Partition (IGMH) method based on the B3LYP/6-311 g (d,p) level for geometry optimization and for single point energy. The conclusions manifest that the weak interactions between these fragments are mainly composed of hydrogen bonds and van der Waals interactions. From the strength of inter-fragment interactions formed by contributing atomic pairs and their percentage contributions, these H bonds, together with dispersion-dominated weak interactions provided by non-direct facing atomic pairs near these H bonds, dominate the inter-fragment interaction resulting in the stability of the molecular structure. Meanwhile, the weak interactions enclosed by end-atoms of two fragments not only include the contributions provided by inter-fragment atomic pairs of two fragments but also include the contributions provided by intra-fragment atomic pairs of fragment 1. For conformation II, due to the H transfer between fragments, a pair of symmetric H bonds at the corresponding regions are extremely strong to reach the level of covalent bond while the two groups −OH at the other end become looser, resulting in conformation II own lower energy. Differences in inter-fragment interactions between two conformations were essentially brought by the stronger electron-withdrawing ability of atom O than that of atom N.     

TET-Like Oxidation in 5-Methylcytosine and Derivatives: A Computational and Experimental Study

The epigenetic marker 5-methylcytosine (5mC) is an important factor in DNA modification and epigenetics. It can be modified through a three-step oxidation performed by ten-eleven-translocation (TET) enzymes and we have previously reported that the iron(IV)-oxo complex [Fe(O)(Py₅Me₂H)]²⁺ ( 1 ) can oxidize 5mC. Here, we report the reactivity of this iron(IV)-oxo complex towards a wider scope of methylated cytosine and uracil derivatives relevant for synthetic DNA applications, such as 1-methylcytosine (1mC), 5-methyl-iso-cytosine (5miC) and thymine (T/5mU). The observed kinetic parameters are corroborated by calculation of the C−H bond energies at the reactive sites which was found to be an efficient tool for reaction rate prediction of 1 towards methylated DNA bases. We identified oxidation products of methylated cytosine derivatives using HPLC-MS and GC-MS. Thereby, we shed light on the impact of the methyl group position and resulting C−H bond dissociation energies on reactivity towards TET-like oxidation.     

CuII Pyrazolyl-Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO₃)(μ-Cl)( L’ )]₂ ( C₁ ) and 22 % of [Cu(NO₃)(μ-NO₃)( L’ )]₂ ( C₂ ), where L was oxidized to a new ligand L^’ . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]₂ ( C₃ ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C₁ and C₂ , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C₃ led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C₁ / C₂ shows remarkable antioxidant activities as compared to the ligand L and reference compounds.     

Design and Expeditious Synthesis of Quinoline-Pyrene-Based Ratiometric Fluorescent Probes for Targeting Lysosomal pH

Intracellular pH plays a significant role in many pathological and physiological processes. A series of quinoline-pyrene probes were synthesized in one-step fashion through an oxonium-ion-triggered alkyne carboamination sequence involving C−C, C−O and C−N bond formation for intracellular pH sensing. The quinoline-pyrenes showed significant red shifts at low pH. Fluorescence lifetime decay measurements of the probes showed decreases in lifetime at pH 4. The probes showed excellent selectivity in the presence of various potential interfering agents such as amino acids and cations/anions. Furthermore, the probes were found to show completely reversible emission behaviour in the window between pH 4 and 7. A morpholine-substituted quinoline-pyrene probe efficiently stained lysosomes with high Pearson correlation coefficients (0.86) with Lysotracker Deep Red DND-99 as a reference. A co-localization study of the probe with Lysotracker DND-99 showed selective intracellular targeting and a shift in fluorescence emission due to acidic lysosomal pH.