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Introduction The aim of this work is to study the thermal behavior in the medium–high temperature range of the sulfur containing amino acid l -cysteine and its corresponding dimer l -cystine, which is composed of two l

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Abstract  

The sulphur-containing proteinaceous amino acids l-cysteine, l-cystine and l-methionine were irradiated in the solid state to a dose of 3.2 MGy. This dose corresponds to that delivered by radionuclide decay in a timescale of 1.05 × 109 years to the organic matter buried at a depth >20 m in comets and asteroids. The purity of the sulphur-containing amino acids was studied by differential scanning calorimetry (DSC) before and after the solid state radiolysis and the preservation of the chirality after the radiolysis was studied by chirooptical methods (optical rotatory dispersion, ORD) and by FT-IR spectroscopy. Although the high radiation dose of 3.2 MGy delivered, all the amino acids studied show a high radiation resistance. The best radiation resistance was offered by l-cysteine. The radiolysis of l-cysteine leads to the formation of l-cystine. The radiation resistance of l-methionine is not at the level of l-cysteine but also l-methionine is able to survive the dose of 3.2 MGy. Furthermore in all cases examined the preservation of chirality after radiolysis was clearly observed by the ORD spectroscopy although a certain level of radioracemization was measured in all cases. The radioracemization is minimal in the case of l-cysteine and is more pronounced in the case of l-methionine. In conclusion, the study shows that the sulphur-containing amino acids can survive for 1.05 × 109 years and, after extrapolation of the data, even to the age of the Solar System i.e. to 4.6 × 109 years.

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Detection of microorganisms in different growth states based on microcalorimetry

A challenging test for establishing a rapid and reliable sterility method

Journal of Thermal Analysis and Calorimetry
Authors: Manrong Tan, Yongsheng Ren, Dan Yan, Xianghong Meng, Longhu Chen, Lingling Qiu, Yan Yan, Jianyu Li, and Xiaohe Xiao

extract, 5 g glucose, 0.5 g l -Cystine, and 0.75 g agar. Medium pH was adjusted to 7.2–7.4 before autoclaving. Then it was sterilized at 121 °C for 30 min, cooled rear, and stored at 4 °C for use. Modified Martin medium [Modified martin medium (MMM), lot

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-0248(01)02135-2 . 5. Meera , K , Muralidharan , R , Santhanaraghavan , P , Gopalakrishnan , R , Ramasamy , P . 2001 . Growth and characterization of l -cystine doped TGS crystals . J Cryst Growth . 226 : 303 – 312 10

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level in environmental samples. Kargosha et al. [ 30 ] reported a novel and selective procedure (by injecting KIO 3 solution) for the determination of l -cysteine and l -cystine, in pharmaceutical and urine samples, based on vapor-generation Fourier

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