Molar Mass Distribution and Chain Conformation of Polysaccharides from Fortunella margarita(Lour.) Swingle

In order to study the effects of different extraction methods on the molar mass distribution and chain conformation of Fortunella margarita （Lour.） Swingle polysaccharides （FP）, we used extraction by hot water （WFP）, ultrasonic-assisted treatment （UFP）, microwave-assisted treatment （MFP） and ultrasonic/microwave-assisted treatment （UMFP）, and then Fourier transform infrared （FT-IR） spectroscopy as well as 1H and 13C nuclear magnetic resonance （NMR） spectroscopy to characterize the structural properties of FP extracted. The molar weight （Mw）, polydispersity index （Mw/Mn）, root-mean-square （RMS） turning radius （Rg）, molar mass distribution and chain conformation of FP were studied systematically using size-exclusion chromatography （SEC）, multi-angle laser light-scattering （MALLS） and refractive index （RI）. WFP, UFP, MFP and UMFP are all typical carbohydrates according to 1H NMR, laC NMR and FT-IR measurements. The type of glycosidic linkage is mainly a fl-glycosidic bond with a small amount of a-glycosidic bond. The results obtained by the SEC-MALLS-RI system showed the molar masses of WFP and UMFP were distributed mainly in the range of 5.0x10^6-1.0x10^7 g-mo1-1 and they accounted for 57.80% and 56.84% of total FP, respectively. The molar masses of UFP and MFP were distributed mainly in the 1.0x10^6-5.0x10^6 g.mol-1 range, which accounted for 38.24% and 52.39% of FP, respectively. WFP and UMFP in water were uniform spherical polymers; UFP and MFP were typical highly branched polymers and the degree of branching for MFP was higher compared to UFP. These results indicated the ultrasonic- and microwave-assisted extraction methods caused a significant decrease of the molar mass of FP but the ultrasonic/microwave synergistic extraction method had no effect.

Cage and ladder structures of silsesquioxanes characterized by UV-MALDI-TOF mass spectrometry

The molar mass distribution of SSO in the first generation derived from the hydrolytic condensation oftwo trialkoxysilanes, [ 3- ( Methacryloxy ) propyl ] trimethoxysilane ( MPMS ) and vinyltrimethoxysilane ( VMS ) ,are determined by UV-MALDI-TOF MS. The comparisons of theoretical masses with experimental masses arecalculated using the proposed compounds, which are assigned to formulas Tn (OH)m, Tn (OMe)y orTn(OH)x(OMe)y[T=RSiO1.5 (x+y)/2n, R=--(CH2)3OOCCH(CH3)CH2 and--CHCH2]. Both theproposed cage and ladder structures of SSO derived from similar sol-gel process of monomers are illustrated. Thecauses for the difference in structures between SSO M and SSO V is discussed as well.