We present a disposable microarray hybridization chamber with an integrated micropump to speed up diffusion based reaction kinetics by generating convective flow. The time-to-result for the hybridization reaction was reduced from 60 min (standard protocol) down to 15 min for a commercially available microarray. The integrated displacement micropump is pneumatically actuated. It includes two active microvalves and is designed for low-cost, high volume manufacturing. The setup is made out of two microstructured polymer parts realized in polycarbonate (PC) separated by a 25 μm thermoplastic elastomer (TPE) membrane. Pump rate can be controlled between 0.3 μl s(-1) and 5.7 μl s(-1) at actuation frequencies between 0.2 Hz and 8.0 Hz, respectively.
Print) 1362-3028 (Online) Journal homepage: http://www.tandfonline.com/loi/tmph20 31 P and 13 C chemical shielding tensors in the phosphoenolpyruvate moiety from rotary resonance recoupling 13 C and 31 P MAS and single crystal 31 A 31P and I3C NMR study of powder and single crystal samples of two phosphoenolpyruvate (PEP) compounds, the tris-ammonium salt monohydrate NH4)3(PEP).H20 (l), and the mono-ammonium-salt (NH4)(H,PEP) (2) is presented. The A P chemical shielding tensors in 1 are measured by 31P single crystal NMR on four minuscule samples and assigned without ambiguity by exploiting the orientation-dependent 31P-31P dipolar splittings of the resonance lines. The orientation of the 31P chemical shielding tensor is discussed in terms of the C2"-and C3-type distortions of the phosphate P04-coordination sphere. From I3C MAS NMR experiments with 31P rotary resonance recoupling on polycrystalline powder samples the orientations of the 31P chemical shielding tensors in l and 2 are obtained, for l in very good agreement with the 31P single crystal NMR results. Only some of the orientational parameters of the three 13C chemical shielding tensors in the PEP moiety of 1 could be derived from 13C MAS NMR experiments with 31P rotary resonance recoupling.
Guanosine triphosphate nucleotide analogues such as GppNHp (also named GMPPNP) or GTPγS are widely used to stabilize rapidly hydrolyzing protein‐nucleotide complexes and to investigate biochemical reaction pathways.Here we describe the chemical synthesis of guanosine 5′‐O‐(γ‐amidotriphosphate) (GTPγNH2) and a new synthesis of guanosine 5′‐O‐(γ‐fluorotriphosphate) (GTPγF). The two nucleotides were characterized using NMR spectroscopy and isothermal titration calorimetry. Chemical shift data on 31P, 19F and 1H NMR resonances are tabulated. For GTPγNH2 the enthalpy of magnesium coordination is ΔH° = 3.9 kcal·mol−1 and the association constant Ka is 0.82 mm−1. The activation energy for GTPγNH2·Mg2+ complex formation is ΔH‡ = 7.8 ± 0.15 kcal·mol−1, similar to that for the natural substrate GTP. For GTPγF we obtained a similar enthalpy of ΔH° = 3.9 kcal·mol−1 while the magnesium association constant is only Ka = 0.2 mm−1. The application of both guanine nucleotide analogues to theGTP‐binding protein Ras was investigated. The rate of hydrolysis of GTPγNH2 bound to Ras protein lay between the rates found for Ras‐bound GTPγS and GppNHp, while Ras‐catalysed hydrolysis of GTPγF was almost as fast as for GTP. The two compounds extend the variety of nucleotide analogues and may prove useful in structural, kinetic and cellular studies.
We demonstrate by selective saturation deuteron NMR experiments on a crystal of selectively deuterated o-terphenyl (OTP) that both end rings I and II attached to the central ring undergo thermally activated flip motions. In crystals of OTP, the end rings I and II are not symmetry related, their dynamics can be different and, in fact, is different, although mutual steric hindrance of the rings suggests a strong correlation. We measured the rates k I and k II of the flips of both end rings I and II as a function of temperature. We find that, independent of the temperature, k I exceeds k II by roughly a factor of 100. This result excludes correlated flips of rings I and II in the sense that a flip of one ring necessarily entails a flip of the other. The activation energies EaI and EaII of the two flip processes turn out to be equal (80.5 kJ mol−1) within experimental errors. This is taken as a hint that the flips are, after all, related to each other. A mechanism is proposed of how this is possible under the constraint k I » k II
In the course of the publication the design, fabrication, and experimental evaluation of a planar microcoil for nuclear magnetic resonance ͑NMR͒ spectroscopy with a 360 m inner diameter integrated to a low-noise metal-semiconductor field-effect transistor is presented. The impedance matching of the coil and transistor was achieved by adjusted coil geometry, while an appropriate microfabrication process including air bridge contacts and a multilayer metal stack was developed for the necessary susceptibility matching of the coil metallization. The NMR spectra of experiments in an 11.75 T magnet ͑corresponding to 500 MHz͒ show the amplification of the signal by the integrated transistor. Due to previous experiments, we wanted to ensure that the whole signal emerged from the sensitive volume of the microcoil.
We present a technology platform suitable for the mass production of laboratory-on-a-chip devices made of polymers with integrated active and passive components. The presented microfluidic platform with integrated valves and pumps for active flow management is realized with three layers consisting of two polymer parts separated by a thin elastic TPE (thermoplastic elastomer) membrane welded together in one step. The elastic TPE membrane acts as an integrated deflectable membrane layer between the two outer polymer layers, each made of a weldable thermoplastic polymer (polycarbonate). Valving is realized by applying pressure in a displacement chamber above a hydraulic channel causing the membrane to deform and to seal the channel. A pump is fabricated using a displacement chamber with a valve on the inlet and outlet. The presented components, namely valve and pump, show excellent behavior regarding response time, sealing quality, and pump rate needing only a low actuation pressure. The three-layer-stack is joined in a single process step by using laser welding, creating devices with high mechanical stability. This production technology fulfills the requirements of a high volume fabrication at high quality and has the potential to manufacture cost-efficient and reliable laboratory-on-a-chip systems. The used materials show a high chemical resistance against a broad range of commonly used liquids and good optical characteristics for the use in μTAS. This consistent technological approach represents a flexible platform for microfluidics with active components to be used in complex applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.