Muhammad Nazir Tahir

Solubility enhancement of α-naphthoflavone by synthesized hydroxypropyl cyclic-(1→2)-β-d-glucans (cyclosophoroases)

Rhizobium leguminosarum produces unbranched cyclic β-1,2-glucans, cyclosophoraoses (Cys). In the present study, Cys were modified with hydroxypropyl groups via a one step chemical derivatization and the complexation ability and solubility enhancement of hydroxypropyl cyclosophoraoses (HP Cys) with α-naphthoflavone (α-NF) were investigated. In the presence of HP Cys, the aqueous solubility of α-NF greatly increased up to 257-fold. Complex formation of HP Cys and α-NF was confirmed by nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Furthermore, the morphological structure of α-NF with HP Cys was examined using scanning electron microscopy (SEM). A hypothetical model was proposed based on molecular dynamics (MD) simulations and a docking study of α-NF with HP Cys. Our results suggest that HP Cys form complexes with α-NF and can be utilized as a promising solubilizer. This is the first study to identify carbohydrates that can enhance the solubility of α-NF.

Immobilisation of β-cyclodextrin on glass: Characterisation and application for cholesterol reduction from milk

β-Cyclodextrin (β-CD) was converted into β-CD-N3 by chemical modification and subsequently attached covalently on glass surface by click reaction. Functionalised glass surface was characterised by static water contact angle and X-ray photoelectron spectroscopy (XPS). Both techniques show that β-CD was successfully attached on glass surface. β-CD on solid surface was used to make a complexation with cholesterol to remove it from milk. 69±1% cholesterol was reduced in 4 h at 25°C and 170 rpm. The same surface was used repeatedly for eight cycles and it maintained its efficiency, with 68±2% cholesterol reduction. Modified glass surface showed almost no degradation as confirmed from XPS analysis after eight cycles of repeated use in cholesterol reduction experiments. The high efficiency and stability of functional monolayer was attributed to its specific structure with relatively low number of functional groups and longer spacer chain length to providing higher flexibility to β-CD molecules.

Biotinylation of the rhizobial cyclic β-glucans and succinoglycans crucial for symbiosis with legumes

The cyclic β-glucans and succinoglycans produced by rhizobia are required for nodulation during symbiosis with legume hosts. However, only gene deletion analyses have been used to investigate their biological importance. For future studies on the physiological activity of those during symbiosis, biochemical methods need to be developed with separate carbohydrate compounds. Here, we isolated and purified rhizobial cellular carbohydrates using various chromatographic methods. Purified cyclic β-glucans, cyclosophoraoses, were monofunctionalized with biotin using the following three steps: tosylation, azidation, and amination. The mono-6-amino-cyclosophoraoses were linked with biotinamidohexanoic acid N-hydroxysuccinimide ester. Succinoglycans and monomers were tagged with biotinamidocaproyl hydrazide at the reducing sugar via reductive amination. The resulting biotinylated rhizobial carbohydrates were characterized by Fourier transform infrared and nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and electrospray ionization mass spectrometry. The resulting neoglycoconjugates can be used as solid probes to study putative plant receptors and for non-invasive imaging for in vivo tracing.

Pentynyl dextran as a support matrix for immobilization of serine protease subtilisin Carlsberg and its use for transesterification of N-acetyl-l-phenylalanine ethyl ester in organic media

In this study, serine protease (subtilisin Carlsberg) was immobilized on pentynyl dextran (PyD, O–alkynyl ether of dextran, 1) and used for the transesterification of N-acetyl-l-phenylalanine ethyl ester (2) with different aliphatic (1-propanol, 1-butanol, 1-pentanol, 1-hexanol) and aromatic (benzyl alcohol, 2-phenyl ethanol, 4-phenyl-1-butanol) alcohols in tetrahydrofuran (THF). The effect of carbon chain length in aliphatic and aromatic alcohols on initial and average transesterification rate, transesterification activity of immobilized enzyme and yield of the reaction under selected reaction conditions was investigated. The transesterification reactivity of the enzyme and yield of the reaction increased as the chain length of the alcohols decreased. Furthermore, almost no change in yield was observed when the immobilized enzyme was repeatedly used for selected alcohols over six cycles. Intrinsic fluorescence analysis showed that the catalytic activity of the immobilized enzyme in THF was maintained due to retention of the tertiary structure of the enzyme after immobilization on PyD (1).

Cholesterol reduction from milk using β-cyclodextrin immobilized on glass.

β-Cyclodextrin (β-CD) was converted into β-CD-undecenyl ether by chemical modification and subsequently covalently attached to a glass surface. The functionalized glass surface was characterized by static water contact angle and x-ray photoelectron spectroscopy. Both techniques confirmed that an excellent monolayer of β-CD was formed on the glass surface. The β-CD solid surface was used to reduce cholesterol levels in milk. In 4h, 73.6% of the cholesterol was extracted at 25°C with shaking at 170rpm. This is the highest value ever reported for milk using β-CD immobilized on a solid surface. The same surface was repeatedly used for 10 cycles and maintained its efficiency with 72±2% cholesterol reduction observed in all the cycles. X-ray photoelectron spectroscopy analysis completed after 5 and 10 cycles of cholesterol reduction showed that the β-CD on the glass surface was not degraded. The high efficiency and long-term stability of the functional monolayer was attributed to the specific structure of β-CD, which is composed of a relatively low number of functional groups and long spacer chain lengths that provide great flexibility.

Pentynyl Ether of β-Cyclodextrin Polymer and Silica Micro-Particles: A New Hybrid Material for Adsorption of Phenanthrene from Water

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyβCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyβCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyβCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyβCD. These results indicate that SMP-PyβCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment.

Mild, Selective Oxidation of Aromatic Alcohols Using β-Cyclodextrin-Functionalized Glass Microparticles: Characterization, Stability, and Application

Abstract The surface of glass microparticle (GMP) was functionalized with β-cyclodextrin (→ GMP-β-CD) and was characterized by x-ray photoelectron spectroscopy (XPS). GMP-β-CD was used to catalyze oxidation of alcohols into aldehydes and katones with excellent yield (86–92%). The modified surface of GMP-β-CD showed no change or degradation after repeated use as confirmed from XPS analysis after 10 cycles. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT