Label-free cell separation and sorting in microfluidic systems

Cell separation and sorting are essential steps in cell biology research and in many diagnostic and therapeutic methods. Recently, there has been interest in methods which avoid the use of biochemical labels; numerous intrinsic biomarkers have been explored to identify cells including size, electrical polarizability, and hydrodynamic properties. This review highlights microfluidic techniques used for label-free discrimination and fractionation of cell populations. Microfluidic systems have been adopted to precisely handle single cells and interface with other tools for biochemical analysis. We analyzed many of these techniques, detailing their mode of separation, while concentrating on recent developments and evaluating their prospects for application. Furthermore, this was done from a perspective where inertial effects are considered important and general performance metrics were proposed which would ease comparison of reported technologies. Lastly, we assess the current state of these technologies and suggest directions which may make them more accessible.     

Chiral Diels–Alder reaction between cyclopentadiene and nitroso derivatives: thermal isomerisation/racemisation of the adducts

Cyclopentadiene nitroso adducts 1a and ent-1a were synthesised in good yields and good enantiomeric excess from chiral chloro-nitroso derivatives 4 and 5 in the d-mannose and d-ribose series, respectively. The thermal racemisation of these adducts occurred below room temperature. Some other chiral Diels–Alder nitroso adducts were prepared in the d-mandelic, l-prolinol and d-O-methylprolinol series and their thermal isomerisation was specified according to the N-substitution. A simple synthesis of the chiral amido-cyclopentenol (+)-2b, an important precursor for biological interesting compounds, is presented from ent-1a.     

Esterification of Polyethylene Glycols

Abstract

Esterification of polyethylene glycols by various carboxylic acids in high yield and high substitution levels is described. The esterification reaction is achieved by dicyclohexylcarbodiimide and catalyzed by dimethylaminopyridine. Rate measurements indicated that the reaction is complete after 2 h at room temperature.     

A Framework for Comparative Evaluation of Dosimetric Methods to Triage a Large Population Following a Radiological Event

BACKGROUND: To prepare for a possible major radiation disaster involving large numbers of potentially exposed people, it is important to be able to rapidly and accurately triage people for treatment or not, factoring in the likely conditions and available resources. To date, planners have had to create guidelines for triage based on methods for estimating dose that are clinically available and which use evidence extrapolated from unrelated conditions. Current guidelines consequently focus on measuring clinical symptoms (e.g., time-to-vomiting), which may not be subject to the same verification of standard methods and validation processes required for governmental approval processes of new and modified procedures. Biodosimeters under development have not yet been formally approved for this use. Neither set of methods has been tested in settings involving large-scale populations at risk for exposure. OBJECTIVE: To propose a framework for comparative evaluation of methods for such triage and to evaluate biodosimetric methods that are currently recommended and new methods as they are developed. METHODS: We adapt the NIH model of scientific evaluations and sciences needed for effective translational research to apply to biodosimetry for triaging very large populations following a radiation event. We detail criteria for translating basic science about dosimetry into effective multi-stage triage of large populations and illustrate it by analyzing 3 current guidelines and 3 advanced methods for biodosimetry. CONCLUSIONS: This framework for evaluating dosimetry in large populations is a useful technique to compare the strengths and weaknesses of different dosimetry methods. It can help policy-makers and planners not only to compare the methods' strengths and weaknesses for their intended use but also to develop an integrated approach to maximize their effectiveness. It also reveals weaknesses in methods that would benefit from further research and evaluation.     

Chiral Atropisomeric 2-Iodo-4,4′,6,6′-tetramethyl-2′-(diphenylphosphoryl)-1,1′-biphenyl-enantiodifferentiation by Rh2[MTPA]4-Adduct Formation and Conformational Analysis

Enantiodifferentiation of the chiral 2-iodo-4,4′,6,6′-tetramethyl-2′-(diphenylphosphoryl)-1,1′-biphenyl (2) can be accomplished easily by adding one mole equivalent of the enantiopure dirhodium complex Rh ^(II) ₂ [(R)-(+)-MTPA]₄ (Rh*). The internal competition of the two bindings sites in 2, the Ph ₂ P═O group, and the iodine atom was identified by variable-temperature ³¹ P NMR. Energy optimization (PM3) and ROESY spectroscopy of 2 in the absence and presence of Rh* reveal that 2 prefers a conformation in the adducts, which is the least stable one in the free molecule, i.e., adduct formation is accompanied by a rotation of the Ph ₂ P═O group about the C-2′─P bond.     

Mechanistic Aspects of the Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling Reaction

The story of C−C bond formation includes several reactions, and surely Suzuki-Miyaura is among the most outstanding ones. Herein, a brief historical overview of insights regarding the reaction mechanism is provided. In particular, the formation of the catalytically active species is probably the main concern, thus the preactivation is in competition with, or even assumes the role of the rate determining step (rds) of the overall reaction. Computational chemistry is key in identifying the rds and thus leading to milder conditions on an experimental level by means of predictive catalysis.     

A PASE-based approach towards 12-(1H-1,2,3-triazol-1-yl)-indolo[2,1-a]isoquinolines via the reaction of 3-(isoquinolin-1-yl)-1,2,4-triazines with benzyne

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Synthesis of N-(Dimethylsulfamoyl)aldimines,a New Type of Aldimine Derivative

N-(Dimethylsulfamoyl)aldimines (3) a new type of shelf-stable aldimine derivatives, are readily prepared from aldehydes and N-(dimethylsulfamoyl)amide (2) in refluxing toluene.