Probing protein binding spectra with fourier microfluidics

Journal ArticleNew developments in microfluidic chip technology enable the construction of chemical spectrum analyzers that can probe the binding interactions between chemical entities. In this paper we report the implementation of a microfluidic chip suitable for Fourier transform measurements of biochemical interactions. The chip consists of a chemical signal generator, a flow cell and a binding sensor surface. The microfluidic signal generator produces a periodic stream of protein plugs in solution flowing at constant velocity through the cell. This flow produces periodic association and dissociation cycles of the protein to a functionalized gold sensing surface placed inside the cell. The sensor activity corresponding to the phasor response of the chemical interaction at the excitation frequency is measured optically using surface plasmon resonance (SPR) imaging. We demonstrated the feasibility of the technique using a model system of carbonic anhydrase-II (CA-II) and immobilized 4-(2- Aminoethyl) benzenesulfonamide (ABS) ligand. The observed transfer function showed a dominant pole at 10.2 mHz corresponding to association and dissociation constants of 4.8 x 103 M-1·s-1, and 3.5 x 10-2 s-1 respectively

Detection of biomolecular binding by fourier-transform SPR

Journal ArticleSurface plasmon resonance (SPR) is a widely used label-free detection technique that has many applications in drug discovery, pharmacokinetics, systems biology and food science. The SPR technique measures the dynamics of a biomolecular interaction at a surface, yielding kinetic association and dissociation constants. Present SPR systems measure the step response of the interaction in time domain hence are subject to time-varying noise disturbances and drifts that limit the minimum-detectable mass changes. This paper presents a new synchronous SPR technique that measures the biomolecular interaction not in time domain, but in frequency domain with a high degree of rejection to uncorrelated spurious signals. The new technique was implemented using a PDMS microfluidic chemical signal modulator chip connected to a set of on-chip functionalized Au SPR sensing sites. Preliminary experimental spectral data for a model system of carbonic anhydrase binding demonstrates the feasibility of the new spectral technique

High resolution simulations of a flash flood near Venice.

Abstract. During the MAP D-PHASE (Mesoscale Alpine Programme, Demonstration of Probabilistic Hydrological and Atmospheric Simulation of flood Events in the Alpine region) Operational Period (DOP, 1 June–30 November 2007) the most intense precipitation event observed south of the Alps occurred over the Venice Lagoon. In the early morning of 26 September 2007, a mesoscale convective system formed in an area of convergence between a south-easterly low level jet flowing along the Adriatic Sea and a north-easterly barrier-type wind south of the Alps, and was responsible for precipitation exceeding 320 mm in less than 12 h, 240 mm of which in only 3 h. The forecast rainfall fields, provided by several convection resolving models operated daily for the D-PHASE project, have been compared. An analysis of different aspects of the event, such as the relevant mechanisms leading to the flood, the main characteristics of the MCS, and an estimation of the predictability of the episode, has been performed using a number of high resolution, convection resolving models (MOLOCH, WRF and MM5). Strong sensitivity to initial and boundary conditions and to model parameterization schemes has been found. Although low predictability is expected due to the convective nature of rainfall, the forecasts made more than 24 h in advance indicate that the larger scale environment driving the dynamics of this event played an important role in favouring the achievement of a relatively good accuracy in the precipitation forecasts

Kawasaki disease in infants less than one year of age : An Italian cohort from a single center

Background and aims Few data are currently available for Kawasaki disease (KD) below 12 months especially in Caucasians. This study aims to analyze clinical and laboratory features of KD among an Italian cohort of infants. Methods A retrospective chart review of KD children aged less than 1 year at time of disease onset between January 2008-December 2017 was performed. Clinical data, laboratory parameters, instrumental findings, treatment and outcome were collected in a customized database. Results Among 113 KD patients, 32 (28.3%) were younger than 1 year. Nineteen patients aged below 6 months, and three below 3 months. The median age was 5.7 +/- 2.7 months. The mean time to diagnosis was 7 +/- 3 days and was longer in the incomplete forms (8 +/- 4 vs 6 +/- 1 days). Conjunctival injection was present in 26 patients (81.2%); rash in 25 (78.1%); extremity changes in 18 (56.2%); mucosal changes in 13 (40.6%,) and lymphadenopathy only in 7 (21.8%). Mucosal changes were the least common features in incomplete forms (18.2%). Twenty-two patients (68.7%) had incomplete KD. Nineteen (59.4%) had cardiac involvement, of whom 13 (59.0%) had incomplete form. ESR, PCR and platelet values were higher in complete KD; especially, ESR resulted significantly higher in complete forms (80 +/- 25.7 mm/h vs 50 +/- 28.6 mm/h; p = 0.01). Conversely, AST level was statistically significant higher in patients with incomplete forms (95.4 +/- 132.7 UI/L vs 29.8 +/- 13.2 UI/L; p = 0.03). All patients received IVIG. Response was reported in 26/32 patients; 6 cases needed a second dose of IVIG and one required a dose of anakinra. Conclusion In our cohort, incomplete disease was commonly found, resulting in delayed diagnoses and poor cardiac prognosis. Infants with incomplete KD seem to have a more severe disease and a greater predilection for coronary involvement than those with complete KD. AST was significantly higher in incomplete forms, thus AST levels might be a new finding in incomplete forms' diagnosis. Eventually, we highlight a higher resistance to IVIG treatment. To our knowledge this is the first study involving an Italian cohort of patients with KD below 12 months

A novel developmental encephalopathy with epilepsy and hyperkinetic movement disorders associated with a deletion of the sodium channel gene cluster on chromosome 2q24.3

We reported a 21 months-old boy with a complex epilepsy phenotype, developmental delay, and hyperkinetic movement disorders, associated with a deletion of the whole sodium channel gene cluster. Whether this unusual phenotype results from leading to haploinsufficiency of either SCN1A or SCN2A, or the combination of both, remains subject of speculation. However, nobody of the numerous reported patients with truncating mutations in SCN1A has ever manifested such a clinical phenotyp

How polymer additives reduce the pour point of hydrocarbon solvents containing wax crystals

We have investigated how four different pour point depressant (PPD) polymers affect the pour point transition in mixtures of a single pure wax in a solvent. We used either n-eicosane (C20), CH3(CH2)18CH3, n-tetracosane (C24), CH3(CH2)22CH3 or n-hexatriacontane (C36), CH3(CH2)34CH3 as the wax component with either n-heptane or toluene as the solvent component. For all wax–solvent combinations, the measured variation of wax solubility with temperature is well predicted by ideal solution theory. The variation of pour point temperature as a function of the overall wax concentration is quantitatively modelled using the idea that, for each overall wax concentration, the pour point occurs at a temperature at which a critical volume fraction ϕ* of wax crystals has precipitated. Close to the pour point temperature, extraction and examination of the wax crystals show they consist of polydisperse, irregularly-shaped platelets with axial ratios (h/d, where h is the plate thickness and d is the plate long dimension) in the range 0.005–0.05. It is found that the measured ϕ* values corresponding to the pour point transitions are weakly correlated with the wax crystal axial ratios (h/d) for all wax–solvent–PPD polymer combinations. These results indicate that the pour point transition occurs at a volume fraction larger than the value at which the volumes of rotation of the platelet crystals overlap, i.e., 2.5(h/d) < ϕ* < 11(h/d). PPD polymers work, in part, by increasing the wax crystal axial ratio (h/d), thereby increasing ϕ* and reducing the pour point temperature. Since the PPD's ability to modify the wax crystal shape relies on its adsorption to the crystal-solution surface, it is anticipated and observed experimentally that optimum PPD efficacy is correlated with the difference between the wax and the polymer solubility boundary temperatures. This finding and the mechanistic insight gained here provide the basis for a simple and rapid screening test to identify candidate species likely to be effective PPDs for particular wax systems