Removal of Dissolved Impurities from Molten Metals

Impurities are transferred out at the boundary of the liquid. Velocities normal to the boundary are small. Therefore, for efficient removal contact areas and times should be large. Transfer depends on the chemical and physical properties of the liquid and the phase that captures the impurities at the boundary. This phase may be a liquid, gas (vacuum) or solid. Properties can be described in terms of equilibrium and empirical mass transfer coefficients. Vacuum may be applied to remove volatile elements. Refining can be carried out by partial solidification or fractional crystallisation, using the segregation that occurs during freezing of an alloy. Finally, an element can be added to form a reactive compound followed by removal of the compound by sedimentation or filtration.

Study of serum malondialdehyde and uric acid levels in patients with malaria

Malaria is parasitic disease of humans caused by parasitic protozoan and genus plasmodium, widely present in tropical region. In the blood, the parasite travel to the liver to mature and reproduce. Oxidative stress is generated through the invasion of malarial parasites in human system. Malondialdehyde is a highly reactive compound is assayed in vivo as a biomarker of oxidative stress. Uric acid contributes to the pathology of human malaria by stimulating the production of cytokines from immune system. To estimate serum MDA & serum uric acid levels in patients with malarial infection and compare same with healthy individuals. This is a cross-sectional observational study, cases and controls were selected using random sampling method, attending hospital OPD. Study includes 50 laboratory diagnosed cases of malaria patients with equal age and sex matched controls. MDA was estimated using MDA - thiobarbituric acid method, uric acid was estimated by phosphotungstic acid method. Standardization of both the methods was carried out prior to experiment. There is generalized increase in serum MDA and uric acid levels in cases as compared to the control group.

Understanding the effect of co-reactants on ketonization of carboxylic acids in the aqueous-phase pyrolysis oil of wood

Ketonization of carboxylic acids is one of the crucial reactions to produce sustainable bio-fuel and bio-chemicals from the pyrolysis oil of wood. Ketonization using different mixed solutions of carboxylic acids, furfural, and hydroxyacetone has been explored to understand the influence of co-feed reactants on the performance of ketonization of carboxylic acid over the selected CeZrOx catalyst. Furfural (7% in water) inhibited the catalytic activity for ketonization of acetic acid (20% solution) with reversible blocking of active sites, but for a mixed solution of hydroxyacetone (7%) and acetic acid (20%), both reactants influenced each other, resulting in very low conversions and slow and uncompleted recovery to 50% after removing hydroacetone from the mixture. For the mixed solution (20% acetic acid + 7% furfural + 7% hydroxyacetone in water), hydroxyacetone was the most reactive compound on CeZrOx and the conversions of reactants reached below 10%, due to the inhibition of co-existing carbonyl components. This work provides guidance for ketonization of carboxylic acids in the aqueous-phase pyrolysis oil.

Aktivitas Antioksidan Kulit, Kitin dan Kitosan Teripang Pasir (Holothuria scabra)

Sea cucumber (H. scabra) has bioactive compounds that are useful as antioxidant. Antioxidant is chemical compound that can donate one or more electrons to free radical. Free radical is reactive compound that have unpaired electrons in the outer shell so it need antioxidant to stabilize. This study aims to determine the content of bioactive compounds and the antioxidant activity on the skin, chitin and chitosan of H. scabra. The analysis parameters observed were bioactive compounds and the antioxidant activity. The results showed that the phytochemical components in skin hexane extract were alkaloids, flavonoids, saponins and steroids/triterpenoids. Chitin contained alkaloids, flavonoids, and saponins. Chitosan contained alkaloid compounds, flavonoids and saponins. IC50 of skin hexane extract and chitin were 1445.05 ppm and 620.07 ppm respectively and included in the very low category. IC50 of chitosan was 235.37 ppm and included in the moderate category. Chitosan had the highest antioxidant activity.

Acyl-CoA thioesterase activity of peroxisomal ABC protein ABCD1 is required for the transport of very long-chain acyl-CoA into peroxisomes

The ABCD1 protein, one of the four ATP-binding cassette (ABC) proteins in subfamily D, is located on the peroxisomal membrane and is involved in the transport of very long chain fatty acid (VLCFA)-CoA into peroxisomes. Its mutation causes X-linked adrenoleukodystophy (X-ALD): an inborn error of peroxisomal β-oxidation of VLCFA. Whether ABCD1 transports VLCFA-CoA as a CoA ester or free fatty acid is controversial. Recently, Comatose (CTS), a plant homologue of human ABCD1, has been shown to possess acyl-CoA thioesterase (ACOT) activity, and it is suggested that this activity is required for transport of acyl-CoA into peroxisomes. However, the precise transport mechanism is unknown. Here, we expressed human His-tagged ABCD1 in methylotrophic yeast, and characterized its ACOT activity and transport mechanism. The expressed ABCD1 possessed both ATPase and ACOT activities. The ACOT activity of ABCD1 was inhibited by p-chloromercuribenzoic acid (pCMB), a cysteine-reactive compound. Furthermore, we performed a transport assay with ABCD1-containing liposomes using 7-nitro-2–1,3-benzoxadiazol-4-yl (NBD)-labeled acyl-CoA as the substrate. The results showed that the fatty acid produced from VLCFA-CoA by ABCD1 is transported into liposomes and that ACOT activity is essential during this transport process. We propose a detailed mechanism of VLCFA-CoA transport by ABCD1.

Untargetted Metabolomic Exploration of the Mycobacterium tuberculosis Stress Response to Cinnamon Essential Oil

The antimycobacterial activity of cinnamaldehyde has already been proven for laboratory strains and for clinical isolates. What is more, cinnamaldehyde was shown to threaten the mycobacterial plasma membrane integrity and to activate the stress response system. Following promising applications of metabolomics in drug discovery and development we aimed to explore the mycobacteria response to cinnamaldehyde within cinnamon essential oil treatment by untargeted liquid chromatography–mass spectrometry. The use of predictive metabolite pathway analysis and description of produced lipids enabled the evaluation of the stress symptoms shown by bacteria. This study suggests that bacteria exposed to cinnamaldehyde could reorganize their outer membrane as a physical barrier against stress factors. They probably lowered cell wall permeability and inner membrane fluidity, and possibly redirected carbon flow to store energy in triacylglycerols. Being a reactive compound, cinnamaldehyde may also contribute to disturbances in bacteria redox homeostasis and detoxification mechanisms.

In Vivo Rate of Formaldehyde Condensation with Tetrahydrofolate

Formaldehyde is a highly reactive compound that participates in multiple spontaneous reactions, but these are mostly deleterious and damage cellular components. In contrast, the spontaneous condensation of formaldehyde with tetrahydrofolate (THF) has been proposed to contribute to the assimilation of this intermediate during growth on C1 carbon sources such as methanol. However, the in vivo rate of this condensation reaction is unknown and its possible contribution to growth remains elusive. Here, we used microbial platforms to assess the rate of this condensation in the cellular environment. We constructed Escherichia coli strains lacking the enzymes that naturally produce 5,10-methylene-THF. These strains were able to grow on minimal medium only when equipped with a sarcosine (N-methyl-glycine) oxidation pathway that sustained a high cellular concentration of formaldehyde, which spontaneously reacts with THF to produce 5,10-methylene-THF. We used flux balance analysis to derive the rate of the spontaneous condensation from the observed growth rate. According to this, we calculated that a microorganism obtaining its entire biomass via the spontaneous condensation of formaldehyde with THF would have a doubling time of more than three weeks. Hence, this spontaneous reaction is unlikely to serve as an effective route for formaldehyde assimilation.

Effects of acetaldehyde-induced DNA lesions on DNA metabolism

Background Acetaldehyde, produced upon exposure to alcohol, cigarette smoke, polluted air and sugar, is a highly reactive compound that is carcinogenic to humans and causes a variety of DNA lesions in living human cells. Previously, we reported that acetaldehyde reacts with adjacent deoxyguanosine residues on oligonucleotides, but not with single deoxyguanosine residues or other deoxyadenosine, deoxycytosine, or thymidine residues, and revealed that it forms reversible intrastrand crosslinks with the dGpdG sequence (GG dimer). Results Here, we show that restriction enzymes that recognize a GG sequence digested acetaldehyde-treated plasmid DNA with low but significant efficiencies, whereas restriction enzymes that recognize other sequences were able to digest such DNA. This suggested that acetaldehyde produced GG dimers in plasmid DNA. Additionally, acetaldehyde-treated oligonucleotides were efficient in preventing digestion by the exonuclease function of T4 DNA polymerase compared to non-treated oligonucleotides, suggesting structural distortions of DNA caused by acetaldehyde-treatment. Neither in vitro DNA synthesis reactions of phi29 DNA polymerase nor in vitro RNA synthesis reactions of T7 RNA polymerase were observed when acetaldehyde-treated plasmid DNA was used, compared to when non-treated plasmid DNA was used, suggesting that acetaldehyde-induced DNA lesions inhibited replication and transcription in DNA metabolism. Conclusions Acetaldehyde-induced DNA lesions could affect the relative resistance to endo- and exo-nucleolytic activity and also inhibit in vitro replication and in vitro transcription. Thus, investigating the effects of acetaldehyde-induced DNA lesions may enable a better understanding of the toxicity and carcinogenicity of acetaldehyde.