Sampling and quantitative analysis of clean B-subtilis spores at sub-monolayer coverage by reflectance Fourier transform infrared microscopy using gold-coated filter substrates
Sampling and quantitative analysis of clean B-subtilis spores at sub-monolayer coverage by reflectance Fourier transform infrared microscopy using gold-coated filter substrates
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DOI：
10.1366/000370208785284358
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发表时间：
2008-08-01
影响因子：
3.5
通讯作者：
Myrick, Michael L.
中科院分区：
文献类型：
--
作者：
Brooke, Heather;Perkins, David L.;Myrick, Michael L.
进行研究以确定细菌孢子的中红外（MIR）吸光度的浓度依赖性。通过傅里叶变换红外（FT-IR）反射显微镜分析了一系列浓度的枯草芽孢杆菌内生孢子通过镀金滤膜过滤。通过自动基线拟合从与酰胺A、酰胺1和酰胺11振动频率相关的峰振幅导出校准曲线，以去除大部分散射贡献。对于所研究的每个频率，在孢子浓度和基线校正峰吸光度之间观察到线性关系（R-2 >= 0.99）。我们的采样面积为100 × 100 μ m（2），酰胺A、酰胺I和酰胺II峰的检测限分别为79、39和184个孢子（或7.92 × 10（5）、3.92 × 10（5）和1.84 × 10（6）孢子/cm（2））。吸光度在散射基线以上线性增加，颗粒表面浓度高达0.9单层（ML）覆盖率，单层密度计算约为1.17 X 10（8）个孢子/cm（2）。作为表面浓度的函数的散射，如从在表现出低吸光度的波长处的消光值估计的，在低得多的表面浓度处变为非线性的。每个孢子的表观散射截面随着浓度的增加而单调下降，而绝对散射在0.9 ML和1.2 ML覆盖范围之间下降。计算表明，横向空间相干效应是这种非线性的起源，而在基线校正吸收的非线性的发病可能是由于多重散射效应，这出现在一个高的表面浓度。测得三个谱带峰值处的吸收截面分别为（2.15 +/- 0.05）× 10（-9）、（1.48 +/- 0.03）× 10（-9）和（0.805 +/- 0.023）× 10（-9）cm（2）。这些值比文献预期值小2-4倍。的起源减少的横截面被假设为是一个电场效应有关的表面选择规则。
A study was conducted to determine the concentration dependency of the mid-infrared (MIR) absorbance of bacterial spores. A range of concentrations of Bacillus subtilis endospores filtered across gold-coated filter membranes were analyzed by Fourier transform infrared (FT-IR) reflectance microscopy. Calibration curves were derived from the peak absorbances associated with Amide A, Amide 1, and Amide 11 vibrational frequencies by automatic baseline fitting to remove most of the scattering contribution. Linear relationships (R-2 >= 0.99) were observed between the concentrations of spores and the baseline-corrected peak absorbance for each frequency studied. Detection limits for our sampled area of 100 X 100 mu m(2) were determined to be 79, 39, and 184 spores (or 7.92 X 10(5), 3.92 X 10(5), and 1.84 X 10(6) spores/cm(2)) for the Amide A, Amide I, and Amide II peaks, respectively. Absorbance increased linearly above the scattering baseline with particle surface concentration up to 0.9 monolayer (ML) coverage, with the monolayer density calculated to be approximately 1.17 X 10(8) spores/cm(2). Scattering as a function of surface concentration, as estimated from extinction values at wavelengths exhibiting low absorbance, becomes nonlinear at a much lower surface concentration. The apparent scattering cross-section per spore decreased monotonically as concentrations increased toward 1.2 ML, while the absolute scattering decreased between 0.9 ML and 1.2 ML coverage. Calculations suggest that transverse spatial coherence effects are the origin of this nonlinearity, while the onset of nonlinearity in the baseline-corrected absorption is probably due to multiple scattering effects, which appear at a high surface concentration. Absorption cross-sections at peaks of the three bands were measured to be (2.15 +/- 0.05) X 10(-9), (1.48 +/- 0.03) X 10(-9), and (0.805 +/- 0.023) X 10(-9) cm(2), respectively. These values are smaller by a factor of 2-4 than expected from the literature. The origin of the reduced cross-section is hypothesized to be an electric field effect related to the surface selection rule.