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1.
Environ Pollut ; 327: 121481, 2023 Jun 15.
Article in English | MEDLINE | ID: mdl-37003584

ABSTRACT

This study is the first report on atmospheric microplastics (MPs) observed in five outdoor environments, including an urban forest, a business center, commercial areas, and a public transportation hub in Seoul, South Korea. Air samples were collected using an active air pump sampler for 24 h in each area only on days without rainfall. All observed microplastics are secondary microplastics, in the form of irregularly-shaped fragments or fibers produced through various degradation processes, rather than being primarily produced like microbeads. The abundance of atmospheric MPs varied depending on the environment (i.e., region, height, and time) from 0.33 to 1.21 MP m-3, with the average number of MPs being 0.72 MP m-3 (standard deviation ± 0.39). MPs in the urban forest was observed to be 27% lower in abundance than that in the urban center which is ∼3 km away. The central business district was observed to have a 25% higher abundance during weekdays than on weekends. Our results show the ubiquity of MPs in various areas from high-rise buildings to forests tens of kilometers away from their direct sources, and a positive correlation between the abundance of MP and human activity. Morphologically, the fragment type (87.4%) predominated over the fiber type (12.6%), and chemically, polypropylene (PP) and polyethylene terephthalate (PET) components accounted for 65% of the total MP. PP polymers were found in all observation sites and contributed to 59% of the total MP fragments. The observed fibrous MPs were mainly composed of PET (72.7%) and PP (18.2%) polymers. Compared to other large cities (Shanghai, Beijing, Paris), Seoul is exposed to low levels of atmospheric MPs and high proportions of PP polymers. This study is limited to atmospheric MPs observed in summer and further investigation of MPs is needed to comprehensively understand the distribution and cycle of MPs based on long-term monitoring of atmospheric MPs.


Subject(s)
Microplastics , Water Pollutants, Chemical , Humans , Plastics , Seoul , Environmental Monitoring , Water Pollutants, Chemical/analysis , China , Republic of Korea , Polypropylenes , Polyethylene Terephthalates
2.
Neurosurg Rev ; 43(4): 1163-1171, 2020 Aug.
Article in English | MEDLINE | ID: mdl-31317284

ABSTRACT

This study aimed to evaluate the safety and completeness of using intraoperative indocyanine green videoangiography (ICGV) combined with intraoperative angiography (IOA) for aneurysm clipping in a hybrid operating room (hOR). All patients who underwent microsurgical clipping in the hOR were identified from prospectively maintained neurosurgical databases. Medical charts and operative videos with ICGV and IOA were reviewed to determine the adequacy of clipping, and clinical and angiographic outcomes were retrospectively analyzed. Fifty-four cerebral aneurysms (ruptured, 31; unruptured, 23) in 50 patients (mean age, 59.4 ± 10.9 y; M:F, 22:28) were evaluated with ICGV and IOA during clipping. Additional IOA led to a clip adjustment during surgery in 9/54 (16.7%) aneurysms for which ICGV had been initially performed. Post-clip perforator compromise occurred in two (3.7%) cases, with a patient with an unruptured aneurysm experiencing permanent injury (grade 3 hemiparesis) and patient with a ruptured aneurysm experiencing transient deficit. Post-clip parent vessel stenosis occurred in one (1.9%) case; however, an ischemic event did not occur because the flow patency was identified by IOA. No other patients with unruptured aneurysms developed new neurologic deficits at discharge. Favorable outcomes (Glasgow Outcome Score [GOS], 4 or 5) were observed in 26/31 patients with ruptured aneurysms. Five patients had unfavorable outcomes (GOS, 2 or 3) from the initial insult. Post-treatment angiography within 1 week showed complete occlusion in 52 (96.3%) aneurysms and minor remnants in two (3.7%) aneurysms. Using combined ICGV and IOA in a hOR may improve the safety and completeness of microsurgical aneurysm clipping.


Subject(s)
Angiography, Digital Subtraction/methods , Cerebral Angiography/methods , Indocyanine Green , Intracranial Aneurysm/surgery , Neurosurgical Procedures/methods , Operating Rooms/organization & administration , Aged , Aneurysm, Ruptured/surgery , Brain Ischemia/etiology , Female , Glasgow Outcome Scale , Humans , Indocyanine Green/adverse effects , Male , Middle Aged , Neurosurgical Procedures/adverse effects , Patient Safety , Postoperative Complications/epidemiology , Reproducibility of Results , Retrospective Studies , Treatment Outcome
3.
Biotechnol Lett ; 32(1): 113-8, 2010 Jan.
Article in English | MEDLINE | ID: mdl-19728106

ABSTRACT

Using site-directed mutagenesis, we investigated the roles of Ile66 and Ala107 of D: -psicose 3-epimerase from Agrobacterium tumefaciens in binding O6 of its true substrate, D: -fructose. When Ile66 was substituted with alanine, glycine, cysteine, leucine, phenylalanine, tryptophan, tyrosine or valine, all the mutants dramatically increased the K (m) for D: -tagatose but slightly decreased the K (m) for D: -fructose, indicating that Ile66 is involved in substrate recognition. When Ala107 was substituted by either isoleucine or valine, the substituted mutants had lower thermostability than the wild-type enzyme whereas the proline-substituted mutant had higher thermostability. Thus, Ala107 is involved in enzyme stability.


Subject(s)
Agrobacterium tumefaciens/enzymology , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Fructose/metabolism , Racemases and Epimerases/chemistry , Racemases and Epimerases/metabolism , Bacterial Proteins/genetics , Enzyme Stability , Kinetics , Molecular Dynamics Simulation , Mutagenesis, Site-Directed , Protein Structure, Secondary , Racemases and Epimerases/genetics , Structure-Activity Relationship , Substrate Specificity
4.
Appl Biochem Biotechnol ; 149(3): 245-53, 2008 Jun.
Article in English | MEDLINE | ID: mdl-18500585

ABSTRACT

Chitopearl beads were used as immobilization supports for D-tagatose production from D-galactose by L-arabinose isomerase from Thermotoga neapolitana because chitopearl beads were more stable than alginate beads at temperatures above 60 degrees C. The pH and temperature for the maximum isomerization of galactose were 7.5 and 90 degrees C, respectively. In thermostability experiments, the half-lives of the immobilized enzyme at 70, 75, 80, 85, and 90 degrees C were 388, 106, 54, 36, and 22 h, respectively. The reaction temperature was determined to be 70 degrees C because the enzyme is highly stable up to 70 degrees C during the reaction. When the reaction time, galactose concentration, and temperature were increased, the pH of a mixture containing enzyme and galactose decreased by the Maillard reaction, resulting in decreased tagatose production. With pH control at 7.5, tagatose production (138 g/L) at 70 degrees C in a stirred tank reactor containing immobilized enzyme and 300 g/L galactose increased two times higher, comparing that without pH control.


Subject(s)
Aldose-Ketose Isomerases/metabolism , Bioreactors , Enzymes, Immobilized/metabolism , Hexoses/biosynthesis , Hydrogen-Ion Concentration , Thermotoga neapolitana/enzymology , Enzyme Stability , Hot Temperature
5.
Appl Environ Microbiol ; 74(8): 2307-13, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18263746

ABSTRACT

An Escherichia coli galactose kinase gene knockout (DeltagalK) strain, which contains the l-arabinose isomerase gene (araA) to isomerize d-galactose to d-tagatose, showed a high conversion yield of tagatose compared with the original galK strain because galactose was not metabolized by endogenous galactose kinase. In whole cells of the DeltagalK strain, the isomerase-catalyzed reaction exhibited an equilibrium shift toward tagatose, producing a tagatose fraction of 68% at 37 degrees C, whereas the purified l-arabinose isomerase gave a tagatose equilibrium fraction of 36%. These equilibrium fractions are close to those predicted from the measured equilibrium constants of the isomerization reaction catalyzed in whole cells and by the purified enzyme. The equilibrium shift in these cells resulted from the higher uptake and lower release rates for galactose, which is a common sugar substrate, than for tagatose, which is a rare sugar product. A DeltamglB mutant had decreased uptake rates for galactose and tagatose, indicating that a methylgalactoside transport system, MglABC, is the primary contributing transporter for the sugars. In the present study, whole-cell conversion using differential selectivity of the cell membrane was proposed as a method for shifting the equilibrium in sugar isomerization reactions.


Subject(s)
Aldose-Ketose Isomerases/metabolism , Cell Membrane/metabolism , Escherichia coli Proteins/metabolism , Escherichia coli/metabolism , Galactose/metabolism , Hexoses/metabolism , Aldose-Ketose Isomerases/isolation & purification , Escherichia coli/enzymology , Escherichia coli/genetics , Escherichia coli/growth & development , Escherichia coli Proteins/genetics , Galactokinase/genetics , Gene Deletion , Kinetics
6.
Biotechnol Prog ; 23(4): 824-8, 2007.
Article in English | MEDLINE | ID: mdl-17583351

ABSTRACT

An L-arabinose isomerase mutant enzyme from Geobacillus thermodenitrificans was used to catalyze the isomerization of D-galactose to D-tagatose with boric acid. Maximum production of D-tagatose occurred at pH 8.5-9.0, 60 degrees C, and 0.4 molar ratio of boric acid to D-galactose, and the production increased with increasing enzyme concentration. Under the optimum conditions, the enzyme (10.8 units/mL) converted 300 g/L D-galactose to 230 g/L D-tagatose for 20 h with a yield of 77% (w/w); the production and conversion yield with boric acid were 1.5-fold and 24% higher than without boric acid, respectively. In 24 h, the enzyme produced 370 g/L D-tagatose from 500 g/L D-galactose with boric acid, corresponding to a conversion yield of 74% (w/w) and a production rate of 15.4 g/L.h. The production and yield of D-tagatose obtained in this study are unprecedented.


Subject(s)
Biotechnology/methods , Boric Acids/chemistry , Hexoses/biosynthesis , Industrial Microbiology/methods , Bacillus/metabolism , Bioreactors , Chromatography, Thin Layer , Enzyme Stability , Galactose/chemistry , Hexoses/chemistry , Hydrogen-Ion Concentration , Mutation , Plasmids/metabolism , Recombinant Proteins , Temperature , Time Factors
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