Studies on Starch Phosphates. Part 3. On the Esterified Phosphates in Some Cereal Starches

Some cereal starches were investigated whether glucose phosphate residues were in the polysaccharides. Significant amounts (6–15 ppm, as P) of glucose 6-phosphate were found in the acid hydrolysates of corn, waxy corn, rice and waxy rice starches. After the extensive action of bacterial α-amylase on these starches phosphorylated oligosaccharide (α-LPD) was recovered in reasonable yield by a DEAE-Sephadex column chromatography. The α-LPDs prepared from two sources of waxy rice starch contained 81.8 and 94,3% of P₀ at the 6th position of glucose residues and the rest of P₀ at the 2nd and/or 3rd positions of glucose residues. All these results show that these starches have glucose phosphate residues. In wheat starch, however, no evidence for the presence of glucose phosphate residues has been obtained.     

Phospholipid-Coated Boronic Oxide Nanoparticles as Boron Agents for Boron Neutron Capture Therapy

Minimally invasive boron neutron capture therapy (BNCT) is an elegant approach for cancer treatment. The highly selective and efficient deliverability of boron agents to cancer cells is the key to maximizing the therapeutic benefits of BNCT. In addition, enhancement of the frequencies to achieve boron neutron capture reaction is also significant in improving therapeutic efficacy by providing a highly concentrated boron agent in each boron nanoparticle. As the density of the thermal neutron beam remains low, it is unable to induce high-efficiency cell destruction. Herein, we report phospholipid-coated boronic oxide nanoparticles as agents for BNCT that can provide a highly concentrated boron atom in each nanoparticle. The current system exhibited in vitro BNCT activity seven times higher than that of commercial boron agents. Furthermore, the system could penetrate cancer spheroids deeply, efficiently suppressing thermal neutron irradiation-induced growth.     

An Attempt to Evaluate the Subsite Structure of Cycloamylose glucanotransferase from Bacillus stearothermophilus: Based on its Transfer Reaction with Substrate Malto-oligosaccharides

Based on determination of the transferred products (maltooligosaccharides G_n), the plausible degradation modes of G₂, G₃, and G₄ were analyzed quantitatively, and it was made an attempt to evaluate the binding affinity A_i on some subsites of cycloamylose glucanotransferase (CGT) from Bacillus stearothermophilus. This method can be employed instead of the technique using a radioisotope. The quantities of the substrates (G₂–G₄) and products G_n were measured by using the HPLC techniques as a function fo time for the CGT-catalysed reaction.     

Study on Specific Modification of Glucosyl Cyclodextrins

The time courses of the periodate oxidation of glucosyl cyclodextrins complexed with organic solvents indicated the preferential oxidation of glucosyl residues on side chains, and the modified cyclodextrins could be purified by using a reversed phase column. HPLC and ¹³C-NMR analyses ensured that the modified cyclodextrins were cyclodextrins having aldehyde residues on their side chains (aldehyde cyclodextrins).     

Studies on Starch Phosphate Part 1. Estimation of glucose-6-phosphate residues in starch and the presence of other bound phosphate(s)

The phosphorus of glucose-6-phosphate residue in starch (P(G6P)) was estimated specifically by means of glucose-6-phosphate dehydrogenase (E.C.1.1.1.49) after acid hydrolysis. Sixty to 70 % of total phosphorus in potato starch was found to be P(G6P)). It was shown that the rest of phosphorus (Px) was incorporated as glucose-2-phosphate and/or glucose-3-phosphate, since it was determined as glucose by periodate oxidation, borohydride reduction, acid hydrolysis and treatment with alkaline phosphatase. The Px was more labile to acid and heat than P(G6P) and decomposed yielding inorganic phosphate. The phospholigosacharide (D. P. 3.6), which was prepared by the limit hydrolysis of potato starch with glucoamylase of Rh. delemar (α-1,4-Glucan glucohydrolase E.C.3.2.1.3) was fractionated by gel-filtration through Sephadex G-25 into fractions with D.P. 2 to 7. Each fraction contained a mole of phosphorus per mole of the saccharide. The P(G6P) and the Px were enriched in the low and the high D.P. fractions, respectively.     

Gas Transport Mechanisms through Molecular Thin Carbon Nanomembranes

Molecular thin carbon nanomembranes (CNMs) synthesized by electron irradiation induced cross-linking of aromatic self-assembled monolayers (SAMs) are promising 2D materials for the next generation of filtration technologies. Their unique properties including ultimately low thickness of ≈1 nm, sub-nanometer porosity, mechanical and chemical stability are attractive for the development of innovative filters with low energy consumption, improved selectivity, and robustness. However, the permeation mechanisms through CNMs resulting in, e.g., an ≈1000 times higher fluxes of water in comparison to helium have not been yet understood. Here, a study of the permeation of He, Ne, D₂, CO₂, Ar, O₂ and D₂O using mass spectrometry in the temperature range from room temperature to ≈120 °C is studied. As a model system, CNMs made from [1″,4′,1′,1]-terphenyl-4-thiol SAMs are investigated. It is found out that all studied gases experience an activation energy barrier upon the permeation which scales with their kinetic diameters. Moreover, their permeation rates are dependent on the adsorption on the nanomembrane surface. These findings enable to rationalize the permeation mechanisms and establish a model, which paves the way toward the rational design not only of CNMs but also of other organic and inorganic 2D materials for energy-efficient and highly selective filtration applications.