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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Adsorption selectivity of sugars toward hydrous zirconium(IV) and hydrous iron(III) oxide surfaces
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Adsorption selectivity of sugars toward hydrous zirconium(IV) and hydrous iron(III) oxide surfaces

机译：糖对水合锆（IV）和水合氧化铁（III）表面的吸附选择性

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摘要

To substantiate stereochemicla interactions between sugars and hydrous metal oxides,a selection of sugars incluing seventeen monosaccharides and sucrose were adsorbed on hydrous zirconium oxide (HZO) and hydrous iron oxide (HIO) suspended in aqueous solutions and their strengths of adsorption where compared according to the Langmuir monolayeradsorption isotherm. Among the eighteen sugars, the largest Langmuir constant a was observed for D- and L-ribose (a = 37 +- 5 and 35.0 +- 0.7, resp.) and the smallest was for #alpha#-methyl-D-glucoside (a = 1.0 +- 0.2). Intermediate values were obtained for mannose, galactose and mannitol (a = 17 +- 2, 18 +- 1 and 16 +- 3, resp.). The configuration of a set of three neighboring hydroxy groups located either on the C(2), C(3) and C(4) carbon atoms of aldoses or on the C(3), C(4) and C(5) carbons of ketoses has a major effect on the Langmuir constant.The strength of adsorption of sugars decreased in the order ax-eq-ax > ax-eq-eq > eq-eq-eq > ~(*)-eq-eq(or~(*)-eq-ax or eq-~(*)-eq), where eq and ax indicated that the respective hydroxy groups are equatorial and axial toward the rings of the sugar molecules, and the asterisk indicates that the hydroxy group is replaced by a H-or CH_3O- group. In addition, it is possible to correlate the order of a values more closely o the geometryof sugar molecules by considering the contribution from all hydroxy groups, together with hemiacetal oxygen atoms in the molecules. The numbers of N_CONF and N_TCSC were counted by manipulating a stereochemical molecular model of sugars and the ratio of R = N_TCSC/N_CONF was calculated; here, N_CONF was the total number of conformations derived from a given sugar molecule and calculated by considering the existence of (i) #alpha#- and #beta#-anomers, (ii) 1C- and C1-conformers, (iii) three rotamers arising from rotations around the C(5)-C(60 bond of aldohexoses and around the C(1)-C(2) bond of ketohexoses. N_TCSC was the number of sets of three oxygen atoms included in the sugar molecule and expected to come close to each other to from a triangle, circumscribed by the smallest circle having an approximate radius of 1.6 +- 0.2 A. The Langmuir constant a was found to be linearly dependent on the ratio R = N_TCSC/N_CONF, the regression line being expressed by the equation a = 28R + 1.
机译：为了证实糖和含水金属氧化物之间的立体化学相互作用，将包含十七个单糖和蔗糖的糖吸附到悬浮在水溶液中的水合氧化锆（HZO）和水合氧化铁（HIO）上，并根据吸附强度进行比较。 Langmuir单层吸附等温线。在18种糖中，对D-和L-核糖观察到最大的Langmuir常数a（分别为a = 37 + -5和35.0 +-0.7），最小的是＃alpha＃-甲基-D-葡萄糖苷（ a = 1.0 +-0.2）。获得了甘露糖，半乳糖和甘露醇的中间值（分别为a = 17 +，2 +，18 + -1和16 + -3）。醛糖的C（2），C（3）和C（4）碳原子上或C（3），C（4）和C（5）碳原子上的三个相邻羟基的集合的配置酮糖的浓度对Langmuir常数有很大影响。糖的吸附强度按以下顺序降低：ax-eq-ax> ax-eq-eq> eq-eq-eq>〜（*）-eq-eq（or〜 （*）-eq-ax或eq-〜（*）-eq），其中eq和ax表示相应的羟基位于糖分子环的赤道和轴向，而星号表示羟基已被取代由H-或CH_3O-组。另外，通过考虑分子中所有羟基以及半缩醛氧原子的贡献，可以使糖分子的几何形状的值的顺序更紧密地相关。通过操纵糖的立体化学分子模型对N_CONF和N_TCSC的数目进行计数，并计算R ＝ N_TCSC / N_CONF的比率。在此，N_CONF是从给定糖分子衍生的构象总数，它是通过考虑以下因素的存在而计算的：（i）＃alpha＃-和＃beta＃-异头物，（ii）1C-和C1构象异构体，（iii）三个绕醛糖己糖的C（5）-C（60键）和酮己糖的C（1）-C（2）键旋转引起的旋转异构体.N_TCSC是糖分子中包含的三个氧原子的集合数彼此接近，由一个半径约为1.6±0.2 A的最小圆所包围的三角形。Langmuir常数a线性依赖于比率R = N_TCSC / N_CONF，回归线为用等式a = 28R + 1表示

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