UV-Laser Ablation Spectroscopy in Element Analysis of Solid Surface

Laser ablation for the atomic emission spectroscopy of a glass sample is studied using pulsed UV laser systems and the effect of the laser wavelength is investigated. The threshold fluence for ablation is decreased and the detection sensitivity is improved for shorter wavelengths. Furthermore, very thin (less than 1 nm/shot) surface slicing is possible at a wavelength as short as 193 nm. Polymers also show good ablation characteristics. Improvement of sensitivity and spatial resolution by using shorter wavelength laser ablation is discussed for Na detection in a glass sample.     

Quantitative Evaluation of Oxygenation and Metabolism in the Human Skeletal Muscle

The forearm muscles of five healthy males were monitored for changes in microvessel hemoglobin saturation (SO_2-TRS) by near infrared time-resolved spectroscopy (NIR_TRS) and changes in phosphorus metabolites by magnetic resonance spectroscopy (³¹P-MRS) during 12 min of resting arterial occlusion. Muscle oxygenation and phosphorus metabolites were also measured during grip exercises at varying intensities. Upon the initiation of occlusion, SO_2-TRS fell progressively until it reached a plateau in the latter half of the occlusion. Phosphocreatine (PCr) began to decrease around 6 min after the initiation of arterial occlusion. The resting O₂ store and O₂ consumption were 295 μM and 0.95 μM/sec, respectively-values which reasonably agree with the reported results. A significant correlation was observed between the changes in SO_2-TRS and PCr during exercise (r² = 0.80, p < 0.001). These results indicate that NIR_TRS is able to provide reliable information about resting metabolism and oxidative rate during exercise. NIR_TRS and MRS are useful to monitor oxygenation and energetics noninvasively in the human muscle.     

Spectroscopic anatomy of molecular-imprinting of cyclodextrin. Evidence for preferential formation of ordered cyclodextrin assemblies.

The processes of molecular-imprinting of beta-cyclodextrin (beta-CyD) with cholesterol and stigmasterol (cross-linking agent = diisocyanate) have been analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy. These templates enormously promote the formation of dimers and trimers of beta-CyD, which are only inefficiently formed in their absence. These ordered assemblies are the guest-binding sites, in which two or three beta-CyD molecules cooperate to bind large steroids. Ordered assemblies are also formed when 2,6-di-O-methyl-beta-cyclodextrin is used in place of beta-CyD. Direct spectroscopic evidence for molecular-imprinting effect has been obtained. Molecular imprinting of CyDs is potent for tailor-made preparation of synthetic receptors for nanometer-scaled guests.     

Natural product-like macrocyclic N-methyl-peptide inhibitors against a ubiquitin ligase uncovered from a ribosome-expressed de novo library

Naturally occurring peptides often possess macrocyclic and N-methylated backbone. These features grant them structural rigidity, high affinity to targets, proteolytic resistance, and occasionally membrane permeability. Because such peptides are produced by either nonribosomal peptide synthetases or enzymatic posttranslational modifications, it is yet a formidable challenge in degenerating sequence or length and preparing libraries for screening bioactive molecules. Here, we report a new means of synthesizing a de novo library of “natural product-like” macrocyclic N-methyl-peptides using translation machinery under the reprogrammed genetic code, which is coupled with an in vitro display technique, referred to as RaPID (random nonstandard peptides integrated discovery) system. This system allows for rapid selection of strong binders against an arbitrarily chosen therapeutic target. Here, we have demonstrated the selection of anti-E6AP macrocyclic N-methyl-peptides, one of which strongly inhibits polyubiqutination of proteins such as p53.     

MALDI-TOF and MALDI-FTICR imaging mass spectrometry of methamphetamine incorporated into hair

A new approach is described for imaging mass spectrometry (IMS) of methamphetamine (MA) incorporated into human hair using matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF) and MALDI-Fourier transform ion cyclotron resonance (FTICR). A longitudinal section of a lengthwise manually-cut single human hair shaft from a chronic MA user was directly analyzed by MALDI-TOF-IMS after deposited with α-Cyano-4-hydroxycinnamic acid matrix. A barcode-like image, which was most probably generated with repeated intakes of MA, was for the first time obtained by monitoring MA-specific product ion in the selected reaction monitoring mode. Laser beam scan lengthwise-cut hair shafts gave only poor mass spectra of MA, probably due to the loss of MA and/or the thermal denaturation of hair. The identity of MA detected in hair was further confirmed by MALDI-FTICR mass spectrometry. A combination with ultra-high resolution mass spectrometry by FTICR provided indisputable identification of MA. The MALDI-FTICR-IMS of another hair shaft from the same MA user also provided a barcode-like image by monitoring the protonated molecule of MA with ultra-high resolution. The two barcode-like images exhibited a close resemblance. Thus, MALDI-IMS can offer a new perspective: 'imaging hair analyses for drugs'.     

Highly sensitive cyanide anion detection with a coumarin-spiropyran conjugate as a fluorescent receptor

A coumarin-spiropyran conjugate (2) shows a CN(-)-selective fluorescence enhancement under UV irradiation. This enables accurate determination of very low levels of CN(-) (>0.5 μM).     

Direct observation of surfactant aggregate behavior on a mica surface using high-speed atomic force microscopy

The processes of dynamic aggregate transformations of micelles at a mica surface were observed using high-speed atomic force microscopy. We showed that salt concentration affects not only the equilibrium state adsorbed structure but also the time required to reach the equilibrium state on the mica surface.