Transient kinetic studies of protein hydrolyses by endo- and exo-proteases on a 27 MHz quartz-crystal microbalance

We have compared endo- and exo-type protease reactions and characterized the enzymatic reaction mechanisms by determining all kinetic parameters (k(on), k(off), k(cat), K(d) = k(off)/k(on), and K(m) = (k(off) + k(cat))/k(on)) by following the mass change of the formation and the decay of the enzyme-substrate (ES) complex (k(on) and k(off)), and the formation of the product (k(cat)) on a 27 MHz quartz-crystal microbalance in aqueous solutions. The K(m) value was nearly equal to the K(d) value for the endo-type protease (subtilisin and alpha-chymotrypsin); however, in the case of exo-type protease (carboxypeptidase P), the K(m) value was quite different from the K(d) value, due to k(cat) > k(off).     

The enantioselective total synthesis of a beta-carboline alkaloid, (S)-(-)-dichotomine C

The first enantioselective synthesis of a beta-carboline alkaloid, dichotomine C, possessing antiallergic effects, was achieved by constructing a beta-carboline framework based on the microwave-assisted thermal electrocyclic reaction of a 1-azahexatriene system, followed by the Sharpless asymmetric dihydroxylation.     

Dynamics of liquid crystalline gelation of DNA

DNA liquid crystalline gel (LCG) films have been prepared by immersing DNA aqueous borate solutions sandwiched between two circular glass plates into cobalt chloride solutions. The time courses of the thickness, the weight fractions of DNA and cobalt cations, and the birefringence and turbidity of the film consisted of outer DNA LCG and inner DNA amorphous gel or solution have been measured. To clarify the mechanism of the process forming LCG, the theory based on the nonequilibrium thermodynamics with "moving boundary picture" [Langmuir 2005, 21, 8155-8160] was modified, and the results were analyzed by the modified theory. It was found that the growth process of DNA LCG consists of two dynamics: cobalt cation diffusion-limited process at the early stage and the DNA circumstance change limited process at the later stage.     

Near-Infrared-III-Absorbing and -Emitting Dyes: Energy-Gap Engineering of Expanded Porphyrinoids via Metallation

The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-Pd^II and bis-Pt^II complexes of hexaphyrin via N-confusion modification led to substantial metal d_π–p_π interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long-wavelength shift of the lowest S₀→S₁ absorption beyond 1700 nm was achieved with the bis-Pt^II complex, t -Pt₂-3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t -Pt₂-3 potentially useful as a NIR-III PA contrast agent. The rigid bis-Pd^II complexes, t -Pd₂-3 and c -Pd₂-3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR-III-emissive and photoacoustic-response capabilities.     

Total synthesis of benzo[c]phenanthridine alkaloids based on a microwave-assisted electrocyclic reaction of the aza 6π-electron system and structural revision of broussonpapyrine

Total syntheses of the des-N-methyl (nor) type of benzo[c]phenanthridine alkaloids 1a-f and 19 and benzo[c]phenanthridine alkaloids, chelerythrine (2d), and broussonpapyrine (2f) were achieved. The key step was the construction of tetracyclic 10,11-dihydrobenzo[c]phenanthridines using a microwave-assisted electrocyclic reaction of the 2-cycloalkenylbenzaldoxime methyl ether 4 as an aza 6π-electron system, which was derived in two steps from a Suzuki-Miyaura cross-coupling reaction of 2-bromobenzaldehyde 6 with 2-(3,4-dihydro-6,7-methylenedioxynaphthyl)boronic acid pinacol ester 7. In addition, the exact structure of broussonpapyrine (2f) (2,3,9,10-tetraoxygenated type) was determined to be chelerythrine (2d).     

Doubly N‐Confused Calix[6]phyrin Bis‐Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation

Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near‐infrared (NIR) region (700 nm≈) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono‐ and bis‐palladium complexes ( 1‐Pd‐H₂ , 2‐Pd‐H₂ , 1‐Pd‐Pd , and 2‐Pd‐Pd ) based on modified calix[6]phyrins as photosensitizers for singlet oxygen generation. These palladium complexes showed intense absorption profiles in the visible‐to‐NIR region (500–750 nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5‐dihydroxynaphthalene (DHN) as a substrate for reactive oxygen species, the bis‐palladium complexes generated singlet oxygen with high efficiency and excellent photostability. Singlet oxygen generation was confirmed from the characteristic spectral feature of the spin trapped complex in the EPR spectrum and the intact ¹O₂ emission at 1270 nm.     

Morphology and properties of globular polymeric materials in the solid state: A composite material of DNA with a cationic surfactant

The aim of the present study was to control entanglements in order to regulate the properties of polymeric solids. Initially, fabrication of polymeric solids with few entanglements was attempted. Films of the DNA–cationic surfactant, cetyltrimethylammonium bromide (CTAB) (DNA–CTA), were cast from ethanol solution at room temperature. Morphological examination of DNA–CTA complex films using atomic force microscopy (AFM) revealed that these films were constructed by particle‐like substances. Geometrical analysis of AFM images showed that the particle‐like substances were the aggregates of several DNA–CTA globules. Mechanical characterization suggested that there were fewer entanglements than with normal plastic films. Small angle X‐ray scattering experiments during annealing indicated that molecular motions were highly excited in the surface region of each particle. In conclusion, a globular polymeric film with fewer entanglements was fabricated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 730–738     

Experimental Correspondence between Spore Dosimetry and Spectral Photometry of Solar Ultraviolet Radiation

Abstract— The biologically effective dose of solar UV radiation was estimated from the inactivation of UV-sensitive Bacillus subtilis spores. Two types of independent measurements were carried out concurrently at the Aerological Observatory in Tsukuba: one was the direct measurement of colony-forming survival that provided the inactivation dose per minute (ID/min) and the other was the measurement of the spectral irradiance by a Brewer spectrophotometer. To obtain the effective spectrum, the irradiance for each 1 nm wavelength interval from 290 to 400 nm was multiplied with the efficiency for inactivation derived from the inactivation action spectrum of identically prepared spore samples. Integration of the effective spectrum provided the estimate for ID/min. The observed values of ID/min were closely concordant with the calculated values for the data obtained in four afternoons in 1993. The average ratio (±SD) between them was 1.24 (±0.16) for 14 data points showing high inactivation rates (<0.05 ID/min). Considering difficulties in the absolute dosimetry of UV radiation, the concordance was satisfactory and improved credibility of the two types of monitoring systems of biologically effective dose of solar UV radiation.     

Efficient stereocontrolled synthesis of sphingadienine derivatives

Sphinga-4,8-dienines, principal long-chain bases of glycolipids in plants and fungi, were efficiently synthesized from l-serine. Hydrozirconation of pentadec-5-en-1-ynes followed by ZnBr₂-catalyzed addition to Garner's aldehyde afforded protected sphinga-4,8-dienines stereoselectively. The (2S,3R,4E,8E)-9-methyl-sphingadienine derivative was then coupled with 2(R)-acetoxypalmitic acid derivative prepared via asymmetric dihydroxylation to give a protected ceramide, which was converted into the corresponding glucocerebroside in two steps.