Characterization of kappa-carageenan from the red alga Kappaphycus striatum

The red alga Kappaphycus striatum is an economically important species and extensively cultivated in Vietnam as a material source for carrageenan production. To evaluate carrageenan quality, the characterization of carrageenan extracted from this alga was investigated. As a result, chemical composition of carrageenan consists of 32.4% of 3,6 anhydrogalactose and 24.3% of sulfate. Gelling and metling temperatures are 34.4oC and 55.6oC, respectively. Gel strength of 1.5% is 615 g/cm2 and average molecular weight is about 267 kDa. Furthermore, FT-IR spectrum showed intense absorption bands at 930 cm-1 and 850 cm-1 that attributed to 1,4-linked 3,6 anhydro-α-D-galactose and 1,3-linked β-D-galactose-4-sulfate of kappa-carrageenan, respectively. 13C NMR spectrum indicated the signals for anomeric carbon of β-D-galactose-4-sulfate at 102.6 ppm and anomeric carbon of 3,6-anhydro-α-D-galactose at 95.3 ppm. 13H NMR spectrum showed peak signals at 3.57 ppm and 5.1 ppm that corresponds with O-methyl proton of 1,3-linked 6-O-methyl-D-galactose and α-anomeric proton of 3,6 anhydro-α-D-galactose residues, respectively. The results show that the carrageenan from the red alga Kappaphycus striatus is kappa-carrageenan with the repeating disaccharide unit consisting of 1,3-linked 6-O-methylated, β-D-galactose-4-sulfate and 1,4-linked 3,6 anhydro-α-D-galactose and did not contain iota-carrageenan. Therefore, this alga may promise to be a good source for carrageenan production for application in food or medicine.

Effect of Active Site Modification towards Performance Enhancement in Biopolymer κ-Carrageenan Derivatives

This research demonstrates a one-step modification process of biopolymer carrageenan active sites through functional group substitution in κ-carrageenan structures. The modification process improves the electronegative properties of κ-carrageenan derivatives, leading to enhancement of the material’s performance. Synthesized succinyl κ-carrageenan with a high degree of substitution provides more active sites for interaction with analytes. The FTIR analysis of succinyl κ-carrageenan showed the presence of new peaks at 1068 cm−1, 1218 cm−1, and 1626 cm−1 that corresponded to the vibrations of C–O and C=O from the carbonyl group. A new peak at 2.86 ppm in 1H NMR represented the methyl proton neighboring with C=O. The appearance of new peaks at 177.05 and 177.15 ppm in 13C NMR proves the substitution of the succinyl group in the κ-carrageenan structure. The elemental analysis was carried out to calculate the degree of substitution with the highest value of 1.78 at 24 h of reaction. The XRD diffractogram of derivatives exhibited a higher degree of crystallinity compared to pristine κ-carrageenan at 23.8% and 9.2%, respectively. Modification of κ-carrageenan with a succinyl group improved its interaction with ions and the conductivity of the salt solution compared to its pristine form. This work has a high potential to be applied in various applications such as sensors, drug delivery, and polymer electrolytes.

Magnetic excitation and readout of methyl group tunnel coherence

Methyl groups are ubiquitous in synthetic materials and biomolecules. At sufficiently low temperature, they behave as quantum rotors and populate only the rotational ground state. In a symmetric potential, the three localized substates are degenerate and become mixed by the tunnel overlap to delocalized states separated by the tunnel splitting νt. Although νt can be inferred by several techniques, coherent superposition of the tunnel-split states and direct measurement of νt have proven elusive. Here, we show that a nearby electron spin provides a handle on the tunnel transition, allowing for its excitation and readout. Unlike existing dynamical nuclear polarization techniques, our experiment transfers polarization from the electron spin to methyl proton spins with an efficiency that is independent of the magnetic field and does not rely on an unusually large tunnel splitting. Our results also demonstrate control of quantum states despite the lack of an associated transition dipole moment.

Isolasi Dan Identifikasi Terpenoid dari Fraksi n-Butanol Herba Lampasau (Diplazium esculentum Swartz)

Abstrak Telah dilakukan penelitian yang bertujuan untuk mengidentifikasi senyawa kimia yang diisolasi dari fraksi n-butanol ekstrak metanol herba lampasau (Diplazium esculentum Swartz). Ekstrak metanol diperoleh secara maserasi dan difraksinasi berturut-turut denganpetroleum eter, etil asetat, dan n-butanol. Fraksi n­-butanol difraksinasidengan kromatografi kolom dengan fase diam silika gel dihasilkan fraksi A, B, C, dan D. Fraksi B dimurnikan dengan kromatografi lapis tipis preparatif pada silika geldihasilkan isolat B1. Isolat B1 berupa padatan tidak berwarna danberfluoresensi putih di bawah lampu UV 366 nm. Panjang gelombang maksimum pada spektra UV isolat B1 adalah 225 nm dan 272.5 nm yang menunjukkan adanya ikatan rangkap tak terkonjugasi. Spektra IR isolat B1 menunjukkan adanya gugus C=C, –OH, C=O lakton, –CO, C–H ulur, dan C–H tekuk. Spektra 1H-NMR isolat B1 menunjukkan sinyal proton pada ikatan rangkap, proton –OH, proton pada –CH2 yang terikat atom oksigen, serta proton gugus metil –CH3. Berdasarkan data spektra UV, IR, dan 1H-NMR maka isolat B1 disarankan sebagai turunan senyawa triterpenoid hopan-lakton. Kata kunci : diplazium esculentum Swartz, fraksi n-butanol, triterpenoid hopan-lakton Abstract The research aims to identify chemical compounds isolated fromn-butanol fraction methanol extract of lampasau herbs (Diplazium esculentum Swartz). The methanol extract was obtained by maceration and fractioned by petroleum ether, ethyl acetate, andn-butanol. N-butanol fraction was fractionated using column chromatography on silica gel produced fractions A, B, C, and D. Fraction B was purified by preparative thin layer chromatography on silica gel produced isolate B1. Isolate B1was colorless solid and has white fluorescent under UV lamp 366 nm. The maximum wavelength on UV spectra of B1 are 225 nm and 272,5 nm indicates the unconjugated double bond. IR spectra of B1 showed the vibration of C=C, –OH, C=O lactone, –CO, C–H stretching and C–H bending. Signals of 1H-NMR spectra of B1 showed the proton of double bond, –OH proton, –CH2 proton bounded on oxygen atom, and –CH3 methyl proton. Based on data of spectra UV, IR, and 1H-NMR, isolate B1 suggested as a hopan triterpen derivative. Keywords : diplazium esculentum Swartz, n-butanol fraction, hopan-lactone triterpene

Formation and stability of organic zwitterions — The carbon acid pKas of the trimethylsulfonium and tetramethylphosphonium cations in water

We report second-order rate constants of kDO = 7.5 × 10–4 and 9.9 × 10–5 (mol/L)–1 s–1 for exchange for deuterium of the first methyl proton of the trimethylsulfonium and tetramethylphosphonium cations, respectively, in D2O at 25 °C and I = 1.0 (KCl). The data were analyzed to give the following carbon acidities for these cationic carbon acids in water: (CH3)3S+, pKa = 28.5; (CH3)4P+, pKa = 29.4. These acidities are close to those of the neutral carbon acids acetonitrile and dimethylacetamide. This provides evidence that a portion of the stabilization of the cyanomethyl carbanion is due to resonance delocalization of negative charge from carbon to cyano nitrogen.Key words: carbon acids, carbanions, ylides, proton transfer.