Shin Mizukami

Anion recognition and anion sensing are of interest because anions play many important roles in living organisms. Most currently known anion sensors work only in organic solution, but sensors for biological applications are required to function in neutral aqueous solution. We have designed and synthesized a novel fluorescent sensor for anions. The sensor molecule 1-Cd(II) contains 7-amino-4-trifluoromethylcoumarin as a fluorescent reporter and Cd(II)-cyclen (1,4,7,10-tetraazacyclododecane) as an

A novel design principle for 19F MRI probes detecting protease activity was developed. This principle is based on 19F MRI signal quenching by the intramolecular paramagnetic effect from Gd3+. The intramolecular Gd3+ dramatically attenuated the 19F probe signal, and the paramagnetic effect was cancelled by the probe hydrolyzation by caspase-3. Using this probe, it was shown that the probe could detect caspase-3 activity spatially from a phantom image using 19F MRI.

When a fluorescent compound shows unique optical properties, an elucidation of the mechanism may lead to an important development of novel sensing strategies. A helical 3,3‘-di-tert-butylsalen−zinc(II) complex, [Zn2L12], has a red-shifted fluorescence as compared to that of [ZnL22], a half-structured mononuclear complex of [Zn2L12]; in addition, [Zn2L12] exhibits a fluorescence color change from green to light blue under external stimulations. We investigated the origins of these phenomena by sp

Techniques for labeling proteins with small molecules have attracted the attention of many life scientists. We have developed a novel protein labeling system that combines a genetically modified, noncatalytic beta-lactamase variant and specific mechanism-based fluorescent probes. Rational design of the tag protein and the labeling probes enables highly specific incorporation of the fluorogen. The feasibility of our approach was confirmed by gel electrophoresis, mass spectrometry, fluorescence sp

Dynamic duo: Magnetic resonance imaging (MRI) can visualize deep regions of living bodies, whereas fluorescence measurement offers excellent sensitivity. These methods thus offer signal enhancement potential for detecting enzyme activities. A dual-mode off/on probe to detect caspase-3 activity by fluorescence and (19)F MRI is presented.

Lanthanide-based luminescent sensors are noteworthy because their long-lifetime luminescence enables time-resolved fluorescence measurements. After exploring suitable antenna groups, we designed and synthesized lanthanide-based luminogenic sensors detecting protease activities. This sensor yielded strong luminescence on addition of proteases such as calpain I and leucine aminopeptidase (LAP). Since the luminescence lifetimes of the probes were very long, the sensors could be applied to time-reso

Microscopic visualization of intracellular enzyme activity can provide information about the physiological role of the enzyme. Caspases are cysteine proteases that have critical roles in the execution of apoptosis. General fluorometric substrates of caspase-3, such as DEVD-MCA, are unsuitable for imaging because they are excited at short wavelength, so we designed and synthesized novel fluorescent probes that are excited at suitable wavelengths for detecting caspase-3 activity in living cells. U

The physiological roles of free Zn(2+) have attracted great attention. To clarify those roles, there has been a need for ratiometric fluorescent Zn(2+) probes for practical use. We report the rational design and synthesis of a series of ratiometric fluorescent Zn(2+) probes. The structures of the probes are based on the 7-hydroxycoumarin structure. We focused on the relationship between the electron-donating ability of the 7-hydroxy group and the excitation spectra of 7-hydroxycoumarins, and exp

The use of genetic engineering techniques allows researchers to combine functional proteins with fluorescent proteins (FPs) to produce fusion proteins that can be visualized in living cells, tissues, and animals. However, several limitations of FPs, such as slow maturation kinetics or issues with photostability under laser illumination, have led researchers to examine new technologies beyond FP-based imaging. Recently, new protein-labeling technologies using protein/peptide tags and tag-specific

Small molecule labeling techniques for cellular proteins under physiological conditions are very promising for revealing new biological functions. We developed a no-wash fluorogenic labeling system by exploiting fluorescence resonance energy transfer (FRET)-based fluorescein-cephalosporin-azopyridinium probes and a mutant β-lactamase tag. Fast quencher elimination, hydrophilicity, and high resistance against autodegradation were achieved by rational refinement of the structure. By applying the p

We describe the first systematic test of steric effects in the active site of a Y-family DNA polymerase, Dpo4. It has been hypothesized that low-fidelity repair polymerases in this family more readily accept damaged or mismatched base pairs because of a sterically more open active site, which might place lower geometric constraints on the incipient pair. We have tested the origin of low fidelity by use of five nonpolar thymidine analogues that vary in size by a total of 1.0 A over the series. Th

The structure of a tetra-coordinated zinc(II) complex with a salen ligand was determined for the first time; unexpectedly, the complex was an interesting 2:2 metal-to-ligand complex.

Imaging of gene expression by magnetic resonance imaging (MRI) yields direct information regarding living systems that cannot be obtained via other methods. In this study, we report the rational design and synthesis of a novel 19F MRI probe that detects β-galactosidase (β-gal) activity, enabling the imaging of gene expression in cells. The 19F MRI signal of the probe was quenched by the intramolecular paramagnetic resonance enhancement from a Gd3+ ion. A contrivance was made in the probe structu

Control of self-assembled nanostructures is a promising technique for nanotechnology. We have examined as to whether nanostructures could be controlled by the size of the central metal ion. Lanthanides are a natural choice for such a study as the size of their trivalent ions changes with atomic number gradually. For this investigation, a series of rare earth complexes ([LaL(1)], [CeL(1)], [SmL(1)], [TbL(1)], [YL(1)], and [LuL(1)]) with a tripodal heptadentate ligand L(1) were synthesized, and th

Better late …︁ Lanthanide-based time-resolved luminescence imaging of proteins is a promising technology. A novel luminescent lanthanide probe (see picture, TPA-Eu) for mutant β-lactamase-based protein labeling system (BL-tag) is used to selectively image cell-surface proteins (POIs) in the presence of autofluorescent background signals, thus enabling imaging with serum. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed