Two-dimensional enzyme diffusion in laterally confined DNA monolayers

Addressing the effects of confinement and crowding on biomolecular function may provide insight into molecular mechanisms within living organisms, and may promote the development of novel biotechnology tools. Here, using molecular manipulation methods, we investigate restriction enzyme reactions with double-stranded (ds)DNA oligomers confined in relatively large (and flat) brushy matrices of monolayer patches of controlled, variable density. We show that enzymes from the contacting solution cannot access the dsDNAs from the top-matrix interface, and instead enter at the matrix sides to diffuse two-dimensionally in the gap between top- and bottom-matrix interfaces. This is achieved by limiting lateral access with a barrier made of high-density molecules that arrest enzyme diffusion. We put forward, as a possible explanation, a simple and general model that relates these data to the steric hindrance in the matrix, and we briefly discuss the implications and applications of this strikingly new phenomenon

Distance optical sensor for quantitative endoscopy.

We present a novel optical sensor able to mea- sure the distance between the tip of an endoscopic probe and the anatomical object under examination. In medical endoscopy, knowledge of the real distance from the endo- scope to the anatomical wall provides the actual dimen- sions and areas of the anatomical objects. Currently, en- doscopic examination is limited to a direct and qualitative observation of anatomical cavities. The major obstacle to quantitative imaging is the inability to calibrate the ac- quired images because of the magnification system. How- ever, the possibility of monitoring the actual size of ana- tomical objects is a powerful tool both in research and in clinical investigation. To solve this problem in a satisfac- tory way we study and realize an absolute distance sensor based on fiber optic low-coherence interferometry FOLCI. Until now the sensor has been tested on pig tra- chea, simulating the real humidity and temperature 37°C conditions. It showed high sensitivity, providing correct and repeatable distance measurements on biologi- cal samples even in case of very low reflected power down to 2t o 3n W, with an error lower than 0.1 mm. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.287013

A method for dynamic subtraction MR imaging of the liver

BACKGROUND: Subtraction of Dynamic Contrast-Enhanced 3D Magnetic Resonance (DCE-MR) volumes can result in images that depict and accurately characterize a variety of liver lesions. However, the diagnostic utility of subtraction images depends on the extent of co-registration between non-enhanced and enhanced volumes. Movement of liver structures during acquisition must be corrected prior to subtraction. Currently available methods are computer intensive. We report a new method for the dynamic subtraction of MR liver images that does not require excessive computer time. METHODS: Nineteen consecutive patients (median age 45 years; range 37–67) were evaluated by VIBE T1-weighted sequences (TR 5.2 ms, TE 2.6 ms, flip angle 20°, slice thickness 1.5 mm) acquired before and 45s after contrast injection. Acquisition parameters were optimized for best portal system enhancement. Pre and post-contrast liver volumes were realigned using our 3D registration method which combines: (a) rigid 3D translation using maximization of normalized mutual information (NMI), and (b) fast 2D non-rigid registration which employs a complex discrete wavelet transform algorithm to maximize pixel phase correlation and perform multiresolution analysis. Registration performance was assessed quantitatively by NMI. RESULTS: The new registration procedure was able to realign liver structures in all 19 patients. NMI increased by about 8% after rigid registration (native vs. rigid registration 0.073 ± 0.031 vs. 0.078 ± 0.031, n.s., paired t-test) and by a further 23% (0.096 ± 0.035 vs. 0.078 ± 0.031, p < 0.001, paired t-test) after non-rigid realignment. The overall average NMI increase was 31%. CONCLUSION: This new method for realigning dynamic contrast-enhanced 3D MR volumes of liver leads to subtraction images that enhance diagnostic possibilities for liver lesions

A method for dynamic subtraction MR imaging of the liver.

none6L. MAINARDI; PASSERA KM; LUCESOLI A; POTEPAN P; SETTI E; MUSUMECI RMainardi, Luca; Passera, Km; Lucesoli, A; Potepan, P; Setti, E; Musumeci, R

Algorithm for reduction of noise in ultramicroscopy and application to near-field microwave microscopy

An approach is introduced to improve the performance of a class of scanning probe microscopy techniques; in principle all techniques exploiting some frequency dependent characteristic could potentially benefit from the proposed approach. Application of the approach in a new near-field microwave microscope setup is reported

Dual-Channel Microwave Scanning Probe Microscopy for Nanotechnology and Molecular Biology

In this work we describe a new dual-channel scanning probe microscope performing simultaneously Scanning Tunneling Microscopy (STM) and wide-band Near Field Scanning Microwave Microscopy (wide-band SMM). Our SMM system exploits the STM feedback to keep a suitable distance between probe and sample. The system is new because our SMM performs broadband measurements of the reflection coefficient across the STM probe by means of an external VNA with no resonant circuit. A post-processing algorithm reduces the noise by comparing images recorded at different close frequencies