• Food Science and Biotechnology
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• 제14권3호
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• pp.317-322
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• 2005

A simple and convenient method of immobilizing dextransucrase via an affinity interaction is described, along with the use of this system to synthesize leucrose. Dextransucrase was produced in sucrose-free medium by fermenting a constitutive mutant of Leuconostoc mesenteroides NRRL B-512F and was separated using an ultrafiltration membrane. The purified enzyme was free of dextran polymer, which previously was always found with the sucrose-induced enzyme. Therefore, it was possible to immobilize the enzyme on dextran-based resins using an affinity interaction. Sephadex G-200 was the best resin for immobilizing the dextransucrase and gave a fast flow rate through the packed column. The immobilized dextransucrase retained more than 80% of its specific activity after immobilization ($K_m\;=\;18.1\;mM$ and $k_{cat}\;=\;450\;sec^{-1}$ vs. 13.1 mM and $640\;sec^{-1}$, respectively, for the free enzyme). The immobilized dextransucrase showed improved stability over a pH range of 4.0 to 6.5 and at moderately high temperatures over $40^{\circ}C$. When immobilized dextransucrase was used to synthesize leucrose via the transfer reaction with sucrose and fructose, about 74% of the sucrose was converted into leucrose after one day, and the half-life of the enzyme activity was 15 days. Regeneration of the resin by supplementation with dextransucrase enabled the recovery of the initial activity of the system, but both the reaction and the flow rate were lower, probably owing to the accumulation of dextran inside the resin.

• Applied Biological Chemistry
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• 제17권2호
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• pp.125-137
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• 1974

Selenomonas ruminantium 균체(菌體)를 TCA로 가열(加熱) 분해(分解)한 후 chloroform : methanol (1 : 3)로 추출(抽出)한 당지질(糖脂質)을 분리(分離)하고 이 당지질(糖脂質)을 acetone가용부분(可溶部分) spot A화합물(化合物)과 acetone불용부분(不溶部分)에서 ether로 다시 가용부분(可溶部分)을 추출(抽出)한 spot B화합물(化合物)의 두 부분(部分)으로 분리(分離)하고 이 두 화합물(化合物)에 대(對)하여 각각(各各) 그 화학구조(化學構造)를 구명(究明)하며 당지질(糖脂質)의 구조(構造)를 추정(推定)한 바 다음과 같은 결과(結果)를 얻었다. 1. 두 화합물(化合物)의 적외선흡수분석결과(赤外線吸收分析結果) spot A는 amino당(糖)에 O-acyl 및 N-acyl지방산(脂肪酸)이 결합(結合)하였으며 spot B는 amino당(糖)에 O-acyl 및 N-acyl지방산(脂肪酸)이 결합(結合)하고 인(燐)을 함유(含有)하고 있음을 알았다. 2. 두 화합물(化合物)을 GLC에 의(依)하여 지방산조성(脂肪酸組成)을 조사(調査)한 바 spot A.B화합물중(化合物中)에 있는 O-acyl 및 N-acyl 지방산(脂肪酸)은 ${\beta}-OH\;C_{13:0}$지방산(脂肪酸)이 대부분(大部分)이 였는데 저급(低級)의 hydroxy지방산(脂肪酸) ${\beta}-OH\;C_{9:0}$도 특이적(特異的)으로 함유(含有)되여 있음을 알았다. 3. 두 화합물(化合物)을 hydrazine분해(分解)를 시킨 결과(結果)를 paper chromatography로 조사(調査)한 바 spot A화합물(化合物)은 glucosamine 이 2분자(分子) 결합(結合)하여 있는 chitobiose와 같은 Rf 치(値)를 나타냈음으로 2분자(分子)의 glucosamine이 결합(結合)됨을 확인(確認)하고 spot B 화합물(化合物)의 낮은 Rf치(値)는 glucosamine에 인(燐)이 결합(結合)되여 있음을 알았다. 4. spotA화합물(化合物)의 산분해물(酸分解物)을 다시 ninbydrine으로 산화분해(酸化分解) 시키면 arabinose만이 생기는 것으로 보아 glucosamine의 amino기(基)는 $C_2$의 위치(位置)에 결합(結合)하여 있음을 알았다. 5. N-acetyl화(化)한 spot A에 $NaBH_4$를 추리(處理)한 결과(結果) glucosamine의 전량(全量)이 반감(半減)하는 것으로 보아 2분자(分子)의 glucosamine이 결합(結合)되여 있는 것을 알 수 있고 Morgan-Elson반응(反應) 및 $NaIO_4$분해(分解)에 의(依)하여 2개(個)의 glucosamine은 1.6결합(結合)임을 확인(確認)하였다. 6. N-acetyl화(化)한 spot A.B화합물(化合物)에 ${\beta}-N-acetyl$ glucosarninidase를 반응(反應)시킨 결과(結果) spot A화합물(化合物)은 100% N-acetyl glucosamine으로 분해(分解)되고 spot B화합물(化合物)은 분해(分解)되지 않았으므로 spot A화합물(化合物)만이 ${\beta}$결합(結合)을 하고 있음을 알았다. 7. $^{32}P$함유(含有) spot B화합물(化合物)에 phosphodiesterase 및 phosphomonoesterase를 작용(作用)시킨 결과(結果) phosphodiesterase는 반응(反應)치 않고 phosphomonoesterase에 의(依)하여 100% $^{32}P$가 유리(遊離)되는 것으로 보아 glucosamine 2분자(分子)에 한계의 인(燐)이 monoester결합(結合)을 하고 있음을 알 수 있다. 8. spot A화합물(化合物)은 glucosaminiyl ${\beta}-1.6-glucosamine$의 결합(結合)을 하였고 O-acyl 및 N-acyl지방산(脂肪酸)이 결합(結合)되여 있으며 주지방산(主脂肪酸)은 ${\beta}-OH\;C_{13:0}$임을 알았다. 9. spot B화합물(化合物)도 glucosaminyl ${\beta}-1.6-glucosamine$의 결합(結合)을 하고 O-acyl 및 N-acyl지방산(脂肪酸)이 결합(結合)되여 있으며 주지방산(主脂肪酸)은 ${\beta}-OH\;C_{13:0}$이나 인(燐)이 monoester결합(結合)을 하고 있는 것이 spot A화합물(化合物)과 특이(特異)함을 알았다.

• Smart Structures and Systems
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• 제4권2호
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• pp.221-232
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• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.