Vibrational spectroscopy differentiates between multipotent and pluripotent stem cells

Over the last few years, there has been an increased interest in the study of stem cells in biomedicine for therapeutic use and as a source for healing diseased or injured organs/tissues. More recently, vibrational spectroscopy has been applied to study stem cell differentiation. In this study, we have used both synchrotron based FTIR and Raman microspectroscopies to assess possible differences between human pluripotent (embryonic) and multipotent (adult mesenchymal) stem cells, and how O(2) concentration in cell culture could affect the spectral signatures of these cells. Our work shows that infrared spectroscopy of embryonic (pluripotent) and adult mesenchymal (multipotent) stem cells have different spectral signatures based on the amount of lipids in their cytoplasm (confirmed with cytological staining). Furthermore, O(2) concentration in cell culture causes changes in both the FTIR and Raman spectra of embryonic stem cells. These results show that embryonic stem cells might be more sensitive to O(2) concentration when compared to mesenchymal stem cells. While vibrational spectroscopy could therefore be of potential use in identifying different populations of stem cells further work is required to better understand these differences.     

Assembly of titanium embedded polyoxometalates with unprecedented structural features

Two titanium embedded polyoxometalates with unprecedented structural features are presented: a monotitanium containing tungstoantimonate Na(13)H(3)[TiO(SbW(9)O(33))(2)]·33 H(2)O featuring a {Ti=O}(2+) moiety (1) and a hexatitanium containing tungstoarsenate K(6)[Ti(4)(H(2)O)(10)(AsTiW(8)O(33))(2)]·30 H(2)O containing a {Ti(4)(H(2)O)(10)}(16+) moiety (2). Both compounds have been fully characterised by single crystal X-ray diffraction, elemental analysis, IR and TGA. 1 is constructed from two α-B-{Sb(III)W(9)O(33)} fragments linked by five sodium cations and an unprecedented square pyramidal Ti(O)O(4) group with a terminal Ti=O bond, and 2 exhibits a Krebs-type structure composed of two {AsTiW(8)O(33)} fragments, where one W(VI) centre has been substituted for a Ti(IV) centre in each, fused together via a belt of four additional Ti(IV) centres. This system represents the tungsten Ti-incorporated polyoxoanion with one of the highest Ti:W ratios so far reported. Additionally, 2 could also be isolated as an n-tetrabutylammonium salt and has been further characterised by electrochemistry and electrospray ionisation (ESI) MS studies. Due to the unique nature of these systems, both have been fully investigated using DFT calculations yielding highly interesting results. Structure 1 has been optimised with five sodium atoms in the belt position, which in addition to reducing the high charge of the cluster influence a stabilisation of the antimony lone pairs. Electrostatic potential calculations highlight the high electronegativity of the terminal oxygen on the titanium centre, enhancing real potentiality as a reactive site for catalysis.     

Structure–Function Relationships in Unsymmetrical Zinc Phthalocyanines for Dye‐Sensitized Solar Cells

Let it shine! The impact of the anchoring group on photovoltaic performance by a series of phthalocyanine sensitisers (see figure) has been demonstrated.

     

Electronic Structure and Redox Properties of Metal Nitride Endohedral Fullerenes M3N@C2n (M=Sc,Y, La,and Gd; 2n=80, 84, 88, 92, 96)

An extensive study of the redox properties of metal nitride endohedral fullerenes (MNEFs) based on DFT computational calculations has been performed. The electronic structure of the singly oxidized and reduced MNEFs has been thoroughly analyzed and the first anodic and cathodic potentials, as well as the electrochemical gaps, have been predicted for a large number of M₃N@C_2n systems (M=Sc, Y, La, and Gd; 2n=80, 84, 88, 92, and 96). In particular, calculations that include thermal and entropic effects correctly predict the different anodic behavior of the two isomers (I_h and D_5h) of Sc₃N@C₈₀, which is the basis for their electrochemical separation. Important differences were found in the electronic structure of reduced M₃N@C₈₀ when M=Sc or when M is a more electropositive metal, such as Y or Gd. Moreover, the changes in the electrochemical gaps within the Gd₃N@C_2n series (2n=80, 84, and 88) have been rationalized and the use of Y‐based computational models to study the Gd‐based systems has been justified. The redox properties of the largest MNEFs characterized so far, La₃N@C_2n (2n=92 and 96), were also correctly predicted. Finally, the quality of these predictions and their usefulness in distinguishing the carbon cages for MNEFs with unknown structures is discussed.     

Regioselective formation of N-alkyl-3,5-pyrazole derived ligands. A synthetic and computational study

New N-alkyl-3,5-pyrazole derived ligands were synthesized by reaction between 3,5-pyrazole derived ligands and the appropriate haloalkane in toluene or THF using NaOEt or NaH as base. When the precursor ligand bears a pyridyl substituent the alkylation reaction presents a large regioselectivity. Theoretical calculations have been carried out to rationalize the experimental observations. It has been shown that regioselectivity is governed by the formation of Na⁺-pyrazolide chelate complexes.     

Texture changes inside smectic-C droplets in azobenzene Langmuir monolayers

Preparation of Langmuir monolayers of a mixture of trans- and cis-isomers of an azobenzene derivative, 4-[4-[(4-octylphenyl)azo]phenoxy]butanoic acid, results in the segregation of birefringent trans-isomer domains embedded in an isotropic medium of cis-isomers. Brewster angle microscopy observations allow us to identify different textures inside the domains depending on surface pressure, temperature, and domain size. The evolution of the monolayer in the dark, from initial droplets formed after spreading to a stable stripe texture, is described. The dynamics of domain coalescence and some morphological transitions induced by temperature and surface pressure changes are also discussed. A simple theoretical model is included to supplement some of these experimental observations.     

Nickel‐Catalyzed Cross‐Coupling of Redox‐Active Esters with Boronic Acids

A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross‐coupling between alkyl‐carboxylic acids and boronic acids is described. This Ni‐catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox‐active ester derivatives, specifically N‐hydroxy‐tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl₂?6 H₂O—$9.5 mol^?1, Et₃N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption.     

The Coordinate Reaction Model: An Obstacle to Interpreting the Emergence of Chemical Complexity

The way chemical transformations are described by models based on microscopic reversibility does not take into account the irreversibility of natural processes, and therefore, in complex chemical networks working in open systems, misunderstandings may arise about the origin and causes of the stability of non-equilibrium stationary states, and general constraints on evolution in systems that are far from equilibrium. In order to be correctly simulated and understood, the chemical behavior of complex systems requires time-dependent models, otherwise the irreversibility of natural phenomena is overlooked. Micro reversible models based on the reaction-coordinate model are time invariant and are therefore unable to explain the evolution of open dissipative systems. The important points necessary for improving the modeling and simulations of complex chemical systems are: a) understanding the physical potential related to the entropy production rate, which is in general an inexact differential of a state function, and b) the interpretation and application of the so-called general evolution criterion (GEC), which is the general thermodynamic constraint for the evolution of dissipative chemical systems.     

Comparison of liquid chromatography-mass spectrometry interfaces for the analysis of polar metabolites of benz[a]pyrene

 The performance of two liquid chromatography-mass spectrometry (LC/MS) interfacing techniques, thermospray (TSP) and atmospheric pressure chemical ionization (APCI), for the analysis of benzo[a]pyrene (BaP) metabolites (hydroxy, epoxy and quinone derivatives) was compared. Interface and detection parameters such as source temperature, eluent composition or flow rate were optimized using negative ion mode. In TSP, the main ions are mostly [M]^-, [M−H₂O]^- or [M+CH₃COO]^-, whereas APCI gives mainly the [M]^- and [M−H]^- ions. Quantification was carried out by flow injection. Calibration graphs were linear in the range of 10 ng to 1000 ng in TSP and 0.1 ng to 10 ng in APCI. Detection limits were in the range of 1 ng to 20 ng in TSP and 0.002 ng to 0.2 ng in APCI. The presence of BaP-1,6-dione, BaP-3,6-dione, and BaP-6,12-dione was confirmed in environmental samples of air particulate matter. Received: 6 January 1997/Accepted: 18 April 1997     

Synthesis of microcin SF608

The first total synthesis of aquatic peptide microcin SF608 is described. Coupling of L-Hpla with the dipeptide L-Phe-L-Choi followed by coupling with agmatine and a deprotection step gave microcin SF608. In addition, the levorotatory character of L-Hpla (5) was thoroughly established, and the conformational analysis of L-Choi containing peptides 1 and 8-10 was performed using NMR spectroscopy to examine the cis-trans isomer equilibrium of the L-Phe-L-Choi amide bond.