THz optical beat-note detection with a fast superconducting hot electron bolometer operating up to 31 GHz

We study the performance of a hot-electron bolometer (HEB) operating at THz frequencies based on superconducting niobium nitride films. We report on the voltage response of the detector over a large electrical detection bandwidth carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.5 K has a 3 dB cutoff around 2 GHz. Remarkably, detection capability is still observed above 30 GHz in an heterodyne beating experiment using a THz quantum cascade laser frequency comb. Additionally, the HEB sensitivity has been evaluated and an optical noise equivalent power NEP of 0.8 pW/√H z has been measured at 1 MHz.

α-Biphenylsulfonylamino 2-methylpropyl phosphonates: Enantioselective synthesis and selective inhibition of MMPs

(R)-alpha-Biphenylsulfonylamino 2-methylpropyl phosphonates attain nM potency against several MMPs and are the most effective inhibitors based on phosphonate as zinc binding group. Since their preparation by direct N-acylation of expensive, enantiopure, alpha-aminophosphonic acids proceeds in low yields, we devised and evaluated a stereoselective and straightforward method of synthesis that avoids the unfavourable step of N-acylation. The key intermediate (R)-4-bromophenylsulfonylamino 2-methylpropyl phosphonate 9 was obtained by highly stereoselective addition of dibenzylphosphite to the enantiopure (S)-N-isobutylidene-p-bromobenzenesulfinamide 3, followed by oxidation with m-CPBA. Suzuki coupling of 9 with the desired arylboronic acids, gave the expected biphenylsulfonylamino derivatives in satisfactory yields. Liberation of the phosphonic group by hydrogenolysis led to the desired (R)-alpha-biphenylsulfonylamino 2-methylpropyl phosphonates 14a-i. Screening of the new compounds on MMP-1, -2, -3, -7, -8, -9, -13 and -14 showed IC(50) in the range of nM in most cases.

Design, synthesis and molecular modeling study of iminodiacetyl monohydroxamic acid derivatives as MMP inhibitors

As the matrix metalloproteinases (MMPs) can be massively up-regulated in degenerative tissues and degrade the extracellular matrix, these key enzymes are promising targets for the therapy of cancer and other degenerative diseases. Here, we are presenting a series of new non-peptidic hydroxamate-based matrix metalloproteinase inhibitors, MMPIs, incorporating the iminodiacetic (IDA) hydroxamic acid scaffold, as mimics of truncated peptidic MMPIs. A series of alkylaryl and sulfonylaryl groups, on the IDA basic scaffold, was investigated with the aim of improving potency and selectivity against MMPs involved in degenerative diseases. The sulfonamide based IDA derivatives studied (compounds B1-B3) showed to be potent (nM range) against deep S1' pocket MMPs enzymes (i.e., MMP-2).

Amber force field implementation, molecular modelling study, synthesis and MMP-1/MMP-2 inhibition profile of (R)- and (S)-N-hydroxy-2-(N-isopropoxybiphenyl-4-ylsulfonamido)-3-methylbutanamides

Ab initio calculations (B3LYP/Lanl2DZ level of theory) were performed in this study to determine all the structural and catalytic zinc parameters required in order to study MMPs and their complexes with hydroxamate inhibitors by means of the AMBER force field. The parameters thus obtained were used in order to study the docking of some known MMPi (Batimastat, CGS 27023A and Prinomastat) and our previously described inhibitor a which had shown an inhibitory activity for MMP-1, and -2, with the aim of explaining the different selectivity. On this basis the two enantiomers (R)-b and (S)-b were designed and synthesized, as more potent MMP-2 inhibitors than our previously described inhibitor a. Between these two enantiomers the eutomer (R)-b proved to be 24.7 times and 15.3 times more potent than CGS 27023A and the parent compound a on MMP-2, maintaining a higher index of MMP-2/MMP-1 selectivity compared with CGS 27023A and the more potent inhibitor Prinomastat. The hydroxamate (R)-b can be considered as a progenitor of a new class of biphenylsulfonamido-based inhibitors that differ from compound a in the presence of an alkyl side chain on the C alpha atom, and show different potency and selectivity profiles on the two MMPs considered.

A new development of matrix metalloproteinase inhibitors: twin hydroxamic acids as potent inhibitors of MMPs

Starting from the observation that the CbzNH(CH2)2 side chain of the potent MMP-2/MMP-14 inhibitor, benzyl-(3R)-4-(hydroxyamino)-3-[isopropoxy(1,1'-biphenyl-4-yl-sulfonyl)amino]-4-oxobutylcarbamate, (R)-1 lies in a hydrophobic region (S1) exposed to the solvent of the protease active site, we hypothesized that an aminoethylcarboxamido chain structurally related to that of (R)-1 might be an useful tool to bind another linker stretching out from the protein. This would be able to interact either with a enzyme region adjacent to the active site, or with other molecules of matrix metalloproteinases (MMPs), or other proteins of the extracellular matrix (ECM) that may be involved in the enzyme activation. On these basis we describe new dimeric compounds of type 2, twin hydroxamic acids, obtained by the joint of two drug entities of (R)-1 linked in P1 by extendable semirigid linkers. Type 2 compounds are potentially able to undergo more complex inhibitor-enzyme interactions than those occurring with monomeric compounds of type 1, thus influencing positively the potency, selectivity and/or cytotoxicity of the new compounds.

N-i-Propoxy-N-biphenylsulfonylaminobutylhydroxamic acids as potent and selective inhibitors of MMP-2 and MT1-MMP

Structural manipulation of the pharmacophoric model of type A selective MMP inhibitors (MMPi), obtained by the insertion of some alkyl substituents R2 possessing an appropriate geometry, steric bulkiness and lipophilicity, is able to improve potency, in the subnanomolar range on MMP-2, and to give a good MMP inhibition on MMP-14 (MT1-MMP) in the designed MMPi of type C, while maintaining a good MMP-1/MMP-2 selectivity profile. The simultaneous inhibition of these two enzymes yields type C compounds, which are potent antiangiogenic agents, able to block a chemoinvasion model on HUVEC cells in the micromolar range.

New N-arylsulfonyl-N-alkoxyaminoacetohydroxamic acids as selective inhibitors of gelatinase A (MMP-2)

New N-arylsulfonyl-substituted alkoxyaminoaceto hydroxamic acid derivatives of types 8 and 10 designed as oxa-analogues of known sulfonamide-based MMPi of types 2 and 7 were synthesized and tested for their inhibitory activities on some matrix metalloproteinases. The combination of a biphenylsulfonamide group with oxyamino oxygen in the pharmacophoric central skeleton of sulfonamide-based MMPi obtained in the new sulfonamides 10 seems to be able to give selectivity for MMP-2 over MMP-1. The most potent derivative of this type, 10a, shows similar anti-invasive properties to the analogue reference drug CGS27023A, 2, in an in vitro model of invasion on matrigel, carried out on cellular lines of fibrosarcoma HT1080 (tumoural cells over-expressing MMP-2 and MMP-9).

Increasing the bandwidth of resonant gravitational antennas: the case of explorer

Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG Collaboration, has been upgraded with a new readout. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its center operating frequency of 919 Hz the spectral sensitivity is better than 10(-20) Hz(-1/2). We describe the detector and its sensitivity and discuss the foreseeable upgrades to even larger bandwidths.

First search for gravitational wave bursts with a network of detectors

We report the initial results from a search for bursts of gravitational radiation by a network of five cryogenic resonant detectors during 1997 and 1998. This is the first significant search with more than two detectors observing simultaneously. No gravitational wave burst was detected. The false alarm rate was lower than 1 per 10(4) yr when three or more detectors were operating simultaneously. The typical threshold was H approximately 4x10(-21) Hz-1 on the Fourier component at approximately 10(3) Hz of the gravitational wave strain amplitude. New upper limits for amplitude and rate of gravitational wave bursts have been set.

Cosmic rays observed by the resonant gravitational wave detector NAUTILUS

The passage of cosmic rays has been observed to excite mechanical vibrations in the resonant gravitational wave detector NAUTILUS operating at temperature of 100 mK. A very significant correlation (more than 10 standard deviations) is found.

A planar second-order DC SQUID gradiometer

In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 microns side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10(-11) T m-2 Hz-1/2 and a field sensitivity of about 2 fT Hz-1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO chi-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described.

Biomagnetic measurements of spontaneous brain activity in epileptic patients

In the last few years there has been an increasing interest in the magnetic activity due to bioelectrical currents flowing in the brain. In this paper preliminary results are reported concerning spontaneous magnetic brain activity in 36 patients affected by different kinds of brain disease; in most of these cases the symptoms were induced by localized pathology (atrophies, scars, tumors). Measurements were carried out with the simultaneous recording of the EEG. At present one of the most interesting features of magnetic detection seems to be its high localizing ability in cases of cortical foci, and sometimes its ability to show activities not evident in the EEG. These features seem to be very encouraging for the search for technical improvements, with the aim of making the magnetic technique a candidate for current diagnostic purposes.