The fatty acids of three strains of extremely thermophilic bacteria and three strains of moderately thermophilic bacteria were examined by gas liquid chromatography. All the thermophiles contained straight, iso, and ante‐iso branched fatty acids. Iso C17∶0 acid was abundant in both the moderately thermophilic strains (10–33%) and the extremely thermophilic strains (50–61%). The pair of fatty acids iso C15∶0 and iso C17∶0 was the predominant pair in both the moderately (34–64%) and extremely (76–87%) thermophilic strains. The pair of fatty acids ante‐iso C15∶0 and ante‐iso C17∶0 was present in larger amount in moderately (25–34%) than in extremely (8.5–15%) thermophilic strains. No hydroxy cyclopropane, or unsaturated fatty acids were found. One extreme thermophile,Flavobacterium thermophilum HB‐8 was grown at 6 different culture temperatures from 49–82 C, and the changes of its fatty acid composition were studied. The ratios of iso C17∶0/iso C15∶0 and ante‐iso C17∶0/ante‐iso C15∶0 were much greater at higher culture temperatures, indicating chain elongation.
The adsorption/desorption mechanisms of biomolecules in porous materials have attracted significant attention because of their applications in many fields, including environmental, medical, and industrial sciences. Here, we employ confocal fluorescence microspectroscopy to reveal the diffusion behavior of zinc myoglobin (ZnMb, 4.4 nm × 4.4 nm × 2.5 nm) as a spherical protein in a single mesoporous silica particle (pore size of 15 nm). The measurement of the time course of the fluorescence depth profile of the particle reveals that intraparticle diffusion is the rate-limiting process of ZnMb in the particle. The diffusion coefficients of ZnMb in the particle for the distribution (D dis ) and release (D re ) processes are determined from the rate constants, e.g., D dis = 1.65 × 10 −10 cm 2 s −1 and D re = 3.68 × 10 −10 cm 2 s −1 , for a 10 mM buffer solution. The obtained D values for various buffer concentrations are analyzed using the pore and surface diffusion model. Although surface diffusion is the main distribution process, the release process involves pore and surface diffusion, which have not been observed with small organic molecules; the mechanism of transfer of small molecules is pore diffusion alone. We demonstrate that the mass transfer kinetics of ZnMb in the silica particle can be explained well on the basis of pore and surface diffusion.
We present a novel analytical principle in which an analyte (according to its concentration) induces a change in the density of a microparticle, which is measured as a vertical coordinate in a coupled acoustic-gravitational (CAG) field. The density change is caused by the binding of gold nanoparticles (AuNP's) on a polystyrene (PS) microparticle through avidin-biotin association. The density of a 10-μm PS particle increases by 2% when 500 100-nm AuNP's are bound to the PS. The CAG can detect this density change as a 5-10 μm shift of the levitation coordinate of the PS. This approach, which allows us to detect 700 AuNP's bound to a PS particle, is utilized to detect biotin in solution. Biotin is detectable at a picomolar level. The reaction kinetics plays a significant role in the entire process. The kinetic aspects are also quantitatively discussed based on the levitation behavior of the PS particles in the CAG field.
The famous solvatochromic Reichardt’s dye was
applied to
quantify hydrostatic pressure in media. The UV/vis spectra of the
dye in various organic solvents are shifted bathochromically or hypsochromically
at the shorter- or longer-wavelength band, respectively, upon hydrostatic
pressurization. The E
T value, determined
by an absorption maximum, in ethyl acetate increases from 38.5 kcal
mol–1 at 0.1 MPa to 39.2 kcal mol–1 at 300 MPa, which is mostly equal to the one in chloroform at 0.1
MPa. These spectroscopic origins were supported by the time-dependent
density functional theory (TD-DFT) calculations. The concept and approach
proposed in this paper, i.e., a dual indicator, should attract the
attention of a broad spectrum in multidisciplinary science.
We propose a scheme for the sensitive quantification of multiple microRNAs (miRNAs) on the basis of the levitation coordinate change (Δz) of single microparticles of different sizes in a coupled acoustic-gravitational (CAG) field. This field transduces the density change of a microparticle into Δz, which can be measured with high precision. The density of a microparticle is induced by the binding of gold nanoparticles (AuNPs) on it through the sandwich DNA hybridization with miRNA. Different probe DNAs are anchored onto microparticles of different sizes, which are clearly distinguishable on a microscopic view. The target miRNAs are captured by these particles having complementary nucleotide sequences and then entrap reporter-anchored AuNPs. Thus, the densities of the microparticles are modified according to the concentration of individual target miRNAs. The interparticle hybridizations for multiple target miRNAs are conducted in one-pot reactions before the levitation of the microparticles is measured in the CAG field. This principle is successfully applied to the quantification of miR-21 and miR-122 in the total RNA extracted from liver cancer tissues.
A novel scheme for DNA sensing at the zeptomole level is presented, based on the levitation of a single microsphere in a combined acoustic-gravitational (CAG) field. The levitation of a microsphere in the field is predominantly determined by its density. Capture and reporter probe DNAs are anchored on poly(methyl methacrylate) microsphere (PMMA) and gold nanoparticles (AuNPs), respectively, and a target DNA induces the binding of AuNPs on PMMA. This interparticle sandwich DNA-hybridization induces density increase in PMMA, which is detected as a shift in the levitation coordinate in the CAG field. The reporter DNAs are designed based on base-pair (bp) number selectivity, which is evaluated using direct interparticle hybridization between DNA-bound PMMA and complementary DNA-anchored AuNPs. Interestingly, the bp-number selectivity can be enlarged by lowering the reactant concentrations. Thus, the threshold bp, at which no density change is detected, can be adjusted by controlling the reactant concentrations. This strategy is extended to the sensing of HIV-2 DNA and single nucleotide polymorphism (SNP) detection of the KRAS gene by sandwich hybridization. In SNP detection, the present method selectively distinguishes wild-type DNA from mutant DNA differing by one nucleotide in the 21-nucleotide sequence by optimizing the lengths of probe DNAs and particle concentrations. This approach allows the detection of 1000 DNA molecules.
Herein, we propose a concept for sensing based on density changes of microparticles (MPs) caused by a biochemical reaction. The MPs are levitated by a combined acoustic-gravitational force at a position determined by the density and compressibility. Importantly, the levitation is independent of the MPs sizes. When gold nanoparticles (AuNPs) are bound on the surface of polymer MPs through a reaction, the density of the MPs dramatically increases, and their levitation position in the acoustic-gravitational field is lowered. Because the shift of the levitation position is proportional to the number of AuNPs bound on one MP, we can determine the number of molecules involved in the reaction. The avidinbiotin reaction is used to demonstrate the effectiveness of this concept. The number of molecules involved in the reaction is very small because the reaction space is small for an MP; thus, the method has potential for highly sensitive detection.
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