• Journal of Microbiology and Biotechnology
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• 제17권8호
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• pp.1291-1299
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• 2007

Two ${\beta}$-1,4-glucanases (DI and DIII fractions) were purified to homogeneity from the culture filtrate of a cellulolytic bacteria, Cellulomonas sp. CS 1-1, which was classified as a novel species belonging to Cellulomonas uda based on chemotaxanomic and phylogenetic analyses. The molecular mass was estimated as 50,000 Da and 52,000 Da for DI and DIII, respectively. Moreover, DIII was identified as a glycoprotein with a pI of 3.8, and DI was identified as a non-glycoprotein with a pI of 5.3. When comparing the ratio of the CMC-saccharifying activity and CMC-liquefying activity, DI exhibited a steep slope, characteristic of an endoglucanase, whereas DIII exhibited a low slope, characteristic of an exoglucanase. The substrate specificity of the purified enzymes revealed that DI efficiently hydrolyzed CMC as well as xylan, whereas DIII exhibited a high activity on microcrystalline celluloses, such as Sigmacells. A comparison of the hydrolysis patterns for pNP-glucosides (DP 2-5) using an HPLC analysis demonstrated that the halosidic bond 3 from the nonreducing end was the preferential cleavage site for DI, whereas bond 2, from which the cellobiose unit is split off, was the preferential cleavage site for DIII. The partial N-terminal amino acid sequences for the purified enzymes were $^1Ala-Gly-Ser-Thr-Leu-Gln-Ala-Ala-Ala-Ser-Glu-Ser-Gly-Arg-Tyr^{15}$-for DI and $^1Ala-Asp-Ser-Asp-Phe-Asn-Leu-Tyr-Val-Ala-Glu-Asn-Ala-Met-Lys^{15}$-for DIII. The apparent sequences exhibited high sequence similarities with other bacterial ${\beta}$-1,4-glucanases as well as ${\beta}$-1,4-xylanases.

• 분석과학
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• 제8권2호
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• pp.139-159
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• 1995

몇 가지 종류의 corticosteroid에 대하여 액체 크로마토그래피-질량분석법으로 양이온 질량 스펙트럼을 얻었다. 화학구조에 따라 수소 첨가된 분자이온 [$MH^+$], 암모늄 첨가이온 [${MNH_4}^+$], 또는 ($MH^+-60$) 이온이 base peak였고 [$MH^+-18$] 또는 [${MNH_4}^+-18$] 이온 등이 특성적으로 나타났다. Methylprednisolone acetate를 male Sprague-Dawley rat에 경구투여한 다음 24시간 동안 배설된 뇨로부터 유리상태 또는 접합상태의 대사물질들을 가수분해, 추출 및 농축하고, thermospray LC/MS를 사용하여 양이온과 음이온 질량토막이온을 분석하였다. Methylprednisolone acetate의 C-21 위치에서의 탈아세틸화(deacetylation), C-20 위치에서 C=0의 -CHOH로의 환원, C-11 위치에서 CHOH의 C=0로의 산화 또는 C-17과 C-20 사이의 bond cleavage등에 의해 생성되는 것으로 추정되는 10여종의 대사물질을 검출하였다. 그 중에 20-hydroxymethylprednisolone(20-HMP), methylprednisolone(MP), methylprednisone(11-KMP)등은 표준물질과 비교 확인하였다.

• 생명과학회지
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• 제14권4호
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• pp.582-588
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• 2004

대전 근교의 농약으로 오염된 토양으로부터 파라치온을 분해하는 81균주를 분리한 후, 분리균주들중 파라치온 이용능이 가장 우수한 한 균주를 최종선별하였다. 최종 선별된 균은 생리생화학적 조사와 16S rRNA 염기 서열분석 등을 통하여 Pseudomonas rhodesiae H5로 확인되었다. Pseudomonas rhodesiae H5는 다양한 당을 이용하였으나 sorbose는 이용하지 못하였다. 또 이 균주는 ampicillin, spectinomycin, mito-mycin C에는 일부 저항성을 가지나 kanamycin, chloram-phenicol에는 저항성을 나타내지 않았다. 그리고 $BaCl_2$, LiCl, $MnSO_4$등의 중금속에서는 mg/ml 단위까지 강한 내성을 나타냈다. Pseudomonas rhodesiae H5의 최적 생장 조건은 3$0^{\circ}C$, pH 7.0 이었고, 이 균주는 파라치온의 organophosphate bond를 가수분해하여 p-nitrophenol를 생성한 후 ortho-ring cleavage를 거쳐 중심대사에 연결되는 것으로 추정된다.

• Journal of Microbiology and Biotechnology
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• 제31권3호
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• pp.464-474
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• 2021

Bacterial cytochrome P450 (CYP) enzymes are responsible for the hydroxylation of diverse endogenous substances with a heme molecule used as a cofactor. This study characterized two CYP154C3 proteins from Streptomyces sp. W2061 (CYP154C3-1) and Streptomyces sp. KCCM40643 (CYP154C3-2). The enzymatic activity assays of both CYPs conducted using heterologous redox partners' putidaredoxin and putidaredoxin reductase showed substrate flexibility with different steroids and exhibited interesting product formation patterns. The enzymatic characterization revealed good activity over a pH range of 7.0 to 7.8 and the optimal temperature range for activity was 30 to 37℃. The major product was the C16-hydroxylated product and the kinetic profiles and patterns of the generated hydroxylated products differed between the two enzymes. Both enzymes showed a higher affinity toward progesterone, with CYP154C3-1 demonstrating slightly higher activity than CYP154C3-2 for most of the substrates. Oxidizing agents (diacetoxyiodo) benzene (PIDA) and hydrogen peroxide (H2O2) were also utilized to actively support the redox reactions, with optimum conversion achieved at concentrations of 3 mM and 65 mM, respectively. The oxidizing agents affected the product distribution, influencing the type and selectivity of the CYP-catalyzed reaction. Additionally, CYP154C3s also catalyzed the C-C bond cleavage of steroids. Therefore, CYP154C3s may be a good candidate for the production of modified steroids for various biological uses.

• Elastomers and Composites
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• 제55권1호
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• pp.51-58
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• 2020

In this study, the thermal oxidation of raw natural rubber (NR) was investigated under controlled conditions by optical image and fourier transform infrared (FT-IR) analysis. The thermal oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 80℃ under low humidity conditions to completely exclude moisture and restrict light oxidation. Images of the thin film of raw NR were obtained before and after thermal oxidation. FT-IR absorption spectra were measured in the transmission mode at different thermal exposure times. The thermal oxidation of NR was examined by the changes in the absorption peaks at 3449, 1736, 1447, 1377, 1242, 1072, and 833 cm^-1, which corresponded to a hydroxyl group (-OH), a carbonyl group (-C=O) from an aldehyde and a ketone, a methylene group (-CH₂-), a methyl group (-CH₃), a carbon-oxygen single bond (-C-O) from an epoxide, a carbon-oxygen bond (-C-O) from an ether, an alcohol, a peroxide, or a cyclic peroxide, and a cis-methine group (cis-CCH₃=CH-), respectively. In the initial stage of thermal oxidation, two different types of free radicals were produced quickly and randomly by the homolytic cleavage of a double bond and allylic hydrogen abstraction. Aldehydes and ketones were formed from chain scissions of the double bonds and alcohols were produced from allylic hydrogen abstraction at the methylene or methyl groups. Two reactions seemed to proceed competitively with each other. At a later stage, oxidative crosslinks seemed to dominate through the combination of free radicals such as an allyl radical (CH=CHCH₂·), alkoxy radical (RO·), and peroxy radical (ROO·) and the reaction of a hydroperoxide (-ROOH) with a double bond. The image obtained after thermal oxidation showed hardening without cracks. Based on these observations, a plausible two-step mechanism was suggested for chain hardening caused by the thermal oxidation.

• KSBB Journal
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• 제15권1호
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• pp.42-48
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• 2000

본 연구에서는 고정화 UK를 이용한 융합단백질의 절단방응에 대해 UK의 고정화, 고정화 UK의 특성과 절단방응, 절단반응 후의 분리정제 그리고 고정화 UK으 재생에 대해 실험하였다. 고정화 수율은 99% 이상이였고 고정화 후의 효소활성은 80%를 유지하였다. 융합단백질 전단반응에서 액상 UK와 고정화 UK를 이용한 회분식 반응 모두 약 70%의 절단반응을 얻었고, 특히 고정화 UK의 사용시 부반응이 매우 낮은 이점이 있었다. 컬럼식 절단반응에서는 기절의 주입속도에 따라 절단수율은 크게 변화하였다. 최적의 유속은 50%의 절단수율을 얻은 1 bed volume/h로 설정하였다. 고정화 효소반응의 이점인 안정성과 반복사용 측면에서는 액상 UK 대비 고정화 UK가 높은 열안정성을 보였고 낮은 pH에서는 10% 이상 높은 활성을 유지하였다. 반복사용을 위해 6M GuHCl을 사용하여 인위적으로 풀림, 재접힘을 한 경우 98%의 활성을 얻음으로 타당성이 있음을 제시하였다. 또한 목적 단백질의 분리를 위하여 산침전 후 expanded bed adsorption 크로마토그래피를 이용함으로써 연속화된 고수율의 정제공정을 가능하게 하였다. 이러한 고정화 UK를 이용한 절단방응 및 정제시스템을 구축함으로써 융합단백지의 생산공정에 매우 유용하게 사용될 것으로 생각되어진다.

• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1711-1716
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• 2005

Fragmentations and ion-molecule reactions of ionized cyclohexane propionic acid and cyclohexane butyric acid were studied using FTMS and theoretical calculations. The difference in bond dissociation depending on the aliphatic chain length was investigated and mechanisms for the possible rearrangements depending on the aliphatic carbon length were suggested. The most abundant fragment ion of the ionized cyclohexane propionic acid was c-$C_6H_{11}CH_2\;^+$ formed from the molecular ion by the direct C-C bond cleavage, while that of the ionized cyclohexane butyric acid was c-$C_6H_9C(OH)=OH^+$ formed by rearrangement of the molecular ion from the acid to diol form and loss of propyl radical. Stabilities of the radical and distonic ions of $C_nH_{2n}O^{+\bullet}$ formed from the molecular ion were compared. Protonated molecules were dissociated into smaller ions by losing one or two water molecules. The $[nM + H]^+$, $[nM + H - H_2O]^+$, and $[nM + H - 2H_2O]^+$ with n = 2 and 3 were generated by solvation with the neutral molecules in the ICR cell at long ion trapping time.

• 대한화학회지
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• 제39권8호
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• pp.598-603
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• 1995

3-피콜린과 파라치환 브롬화벤질류의 반응을 온도와 압력 및 치환기 변화에 따라 속도론적으로 연구하였다. 속도상수로부터 활성화 파라미터들과 Hammett .rho.값을 계산하였다.결과적으로 반응중심에는 양의 전하가 진전되고 결합형성 보다는 결합파괴가 촉진됨을 알 수 있었다. 압력증가에 따라 반응 속도와 전하이동능력은 증가하고, 낮은 온도에서의 전하이동에 대한 압력효과가 더욱 크게 작용하고 있음을 알 수 있다.

• 한국의류학회지
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• 제13권1호
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• pp.59-66
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• 1989

This paper is concerned with formaldehyde release from durable press finished rayon fabrics. $100\%$ rayon fabrics were treated with 3 kinds of commercial N-methylol crosslinking agents using a pad-dry cure technique. Aqueous extractions of fabric samples were carried out at $40^{\circ}C$ under pH's of 4, 7, 10. Formaldehyde release was evaluated for the types of resins, catalyst concentrations and extraction conditions. Results indicated that the higher concentration of catalyst leads to the more fixation of resin on the fabric. Total formaldehyde released to the extract was decreased as the catalyst concentration increased. For the resin types, the amount of formaldehyde released was in the order of DMU>MDMDHEU>DMDHEU. Free formaldehyde content in the extract was in the order of pH10>pH4>pH7. This result proved that resins are least resistant to alkaline hydrolysis and the N-C bond cleavage under alkaline condition. Under acidic condition, however, N-methylol formaldehyde was accumulated before the release of free formaldehyde. This suggested the C·0 bond cleavalge to form carbonium - immonim intermediate.

• 대한화학회지
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• 제25권4호
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• pp.207-213
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• 1981

티오아세트 아미드(TAA)의 형태와 양성자화된 TAA의 형태를 CNDO/2 방법으로 결정하고 물분자 접근시의 분자간 상호작용 에너지를 계산하였다. 양성자는 S원자보다는 N원자에 첨가되는 것이 안정하며 또 물분자가 접근 할때의 안정화에너지도 N-양성자화된 TAA에서 컸다. 이때는 CS결헙의 LUMO의 강한 반결합성 때문에 우선적인 CS 절단으로 반응이 진행되며 orbital controlled 반응 임을 알았다.