Effects of Macromolecular Crowding on Model in vitro Antigen-Antibody Reactions
Many biological processes in the human body take place in intracellular environments under crowded conditions. This means that such cellular activities occur in the presence of inert macromolecules. These macromolecules are thought to have large effects on reaction rates and equilibria. However, under conventional conditions, these same processes are studied in vitro under uncrowded conditions in dilute buffers and therefore not reflective of physiological conditions. Hence, this project aims to study the effect of macromolecular crowding on antigen-antibody reactions in an attempt to mimic intracellular environments. It also aims to highlight the importance of introducing crowders as a factor of study in conventional in vitro experiments involving cellular reactions. The model reaction investigated involves human collagen type 1 on skin samples and specific antibodies against these antigens. Inert macromolecules of defined hydrodynamic radius and charge were added into the reaction media while quantitative tests are conducted to determine the effect of crowding on the rate and extent of reaction. The macromolecular crowders used were Dextran Sulphate, Ficol170, Ficol1400 and Polyvinylpyrrolidone360. Results were than analysed with the Metamorph 7 imaging system to determine signal strength under crowded and non-crowded conditions. At high primary antibody dilutions, skin samples incubated with a primary antibody solution crowded with a combination of inert macromolecules showed improve signal strength. This could be because crowding tends to shift reaction equilibria such as to minimise the amount of excluded volume, leading to association of the antigen and its specific antibody. This is known as the excluded volume effect. In addition, crowding the primary antibody solution helped increase the rate of reaction. The results also suggest that the addition of crowders may reduce the amount of antibodies needed per sample and decrease the necessary incubation time. Therefore, antigen-antibody reactions can be done more cost-effectively, However, the presence of charged macromolecules such as Dextran Sulphate has an inhibitory effect. Further work is also needed to establish whether macromolecular crowding enhances specificity and thereby reduce autoflourescence of the skin sample.
Mechanism of the subcellular localization of the actin binding protein adducin
Adducin蛋白在細胞骨架的調節上扮演著重要的角色。然而,近來有許多研究指出,骨架蛋白也會出現在細胞核並參與轉錄調控,因此本研究的目的即在探討adducin蛋白是否會進入細胞核中,並參與轉錄調控或具有其他功能。在本研究中,我們將綠色螢光蛋白(GFP)標示的adducin質體DNA,利用轉染技術送入老鼠纖維母細胞株NIH3T3中表現。NIH3T3細胞原本並無adducin蛋白的表現,在共軛焦顯微鏡下觀察,野生型的GFP-adducin蛋白會表現於細胞核與細胞質中。由於adducin蛋白尾端序列攜有可能往核內運輸的訊號,於是將位在此一訊號中的離胺酸718及離胺酸719進行突變,結果發現此一突變株只能在細胞質中表現。此外,蛋白磷酸脢C(protein kinase C)已知能磷酸化adducin蛋白在絲胺酸716及絲胺酸726的位置,於是假設其磷酸化是否與其在細胞內的分布有關。將adducin的絲胺酸726置換成丙胺酸,並不影響其在細胞內的分布。然而將絲胺酸716置換成丙胺酸後,則完全只在細胞核中表現。由於adducin可分布於細胞核,因此我們懷疑adducin蛋白可能與細胞分裂有關,於是本研究利用流式細胞儀分析adducin轉染後NIH3T3細胞的細胞週期。流式細胞儀的分析結果顯示,攜有GFP-adducin或其突變株的細胞與未經轉染的NIH3T3細胞的細胞週期並沒有顯著差異。其次,為了避免因轉染的效率不高而造成統計上的誤差,我們利用顯微鏡追蹤技術觀察攜有GFP-adducin的細胞株,結果顯示攜有adducin突變株的NIH3T3細胞株仍能正常分裂。再者,因為adducin能與細胞骨架中的肌動蛋白結合,所以adducin不同的分布位置可能影響細胞附著與細胞展延的效率。細胞展延試驗的結果顯示,adducin及其突變株對細胞附著與細胞展延的效率並無明顯的影響。本研究的結果證明,adducin的確帶有往核內運輸的訊號,其在細胞質中的分布可能也同時受到絲胺酸716磷酸化的影響。然而adducin的功用似乎與纖維母細胞的分裂與展延無明顯的關聯性。Adducin, an actin binding protein, is known to play an important role in the regulation of the membrane cortical cytoskeleton. More and more evidence indicates that proteins involved in the cytoskeletal regulation could also reside in the nucleus and participate in gene regulation. Thus, the goal of this study is to examine whether adducin is expressed in the nucleus and involved in certain nuclear events. In this study, adducin and its various mutants were fused with green fluorescent protein (GFP) and transfected into mouse NIH3T3 fibroblasts which do not have endogenous adducin for monitoring their subcellular distribution under a laser scanning confocal microscope. The wild-type GFP-adducin was found to be present both in the nucleus and in the cytoplasm. The COOH-tail of adducin contains a motif analogous to the nuclear localization signal (NLS). Mutation of two lysine residues (lysine 718 and lysine 719) located within this motif abolished the nuclear localization of adducin. Moreover, adducin is known to be phosphorylated by protein kinase C at serine 716 and 726. Substitution of adducin serine 726 with alanine had no effect on its subcellular localization. In contrast, substitution of adducin serine 716 with alanine led to only nuclear expression. Nuclear localization of adducin renders it possible that adducin may be involved in the regulation of cell division cycle. For cell cycle analysis, flow cytometry was applied. The results of flow cytometry indicated that expression of adducin and its mutants in NIH3T3 fibroblasts did not affect their cell cycle progression. To further examine the effect of adducin on cell division, NIH3T3 cells transiently transfected by adducin were monitored by time lapse video microscopy. The video clearly showed that the cells with GFP-adducin underwent cell division to generate two daughter cells. Since adducin is well known to bind to actin and thereby regulate microfilaments, we wondered that expression of adducin in NIH3T3 cells might affect their adhesion and spreading onto extracellular matrix proteins. The results of cell spreading assays showed that adducin appeared not to affect cell spreading. In conclusion, our results demonstrate that the subcellular distribution of adducin is likely regulated by two signals, one is the nuclear localization signal and the other is the phosphorylation status of the serine 716. However, enforced expression of exogenous adducin in fibroblasts such as NIH3T3 cells does not alter their cell cycle or cell spreading on fibronectin.
竹嵌紋病毒及其衛星核酸5'端非轉譯區與複製競爭關係之探討
RNA 病毒在複製過程中容易產生錯誤,導致其族群具中有很大的遺傳歧異度,累積的錯誤再加上選汰的壓力造成往後之變異。由於RNA 基因體之病毒變異較大,使得RNA 病毒在單一寄主上具有quasispecies 的特性,提供病毒產生新基因體的機會以適應環境或演化成新病毒。例如流行性感冒病毒與之前造成恐慌的嚴重急性呼吸道症候群病毒(severe acute respiratorysyndrome,SARS)以及禽流感病毒 (avain influenza virus) 皆為RNA 病毒,意味著RNA 病毒知不穩定性,並容易造成一些目前我們無法及時反應的危害。大部分的植物病毒又為RNA 病毒,本研究將以竹嵌紋病毒 ( Bamboo mosaic virus , BaMV )及其衛星核酸 (satellite RNA, satBaMV)為材料,進一步探討核?酸序列之變異對其族群在複製競爭上的影響。
愛的教育,鐵的紀律-果蠅的學習與記憶
The main purpose of this study is to explore whether fruit flies (Drosophila melanogasters which background is 2U) can distinguish and memorize different colors and smells by learning. Futhermore, to find out the relation between age and learning ability, and analyze the influence of repeated training on how long the memory would last. According to our experiment, in smell training, the fruit flies are able to distinguish and memorize different smells, and young fruit flies have better memory than old flies. In color training, the fruit flies can distinguish and memorize different colors, but the effect was less than that of smell training. In intensive learning, proper times of learning increased the memory ability, but excessive learning exhibited an opposite effect. In the labyrinth experiment, we select and nurture the fruit flies having the best color memory in order to further understand the gene correlated with the memory learning. In addition, in one-time training, fruit flies are able to remember the smells and colors in four minutes, and young ones have the better ability. In six-time training, fruit flies have the ability to remember the smells and colors in twelve minutes. In the end, we hope you can know more about the learning and memory ability of fruit flies through our report. 本實驗主要探討果蠅是否可經由學習分辨、記憶顏色與氣味,並探討年齡與學習能力的相關性、分析多次訓練對記憶時間的影響。由實驗結果得知,氣味方面,果蠅有辨識記憶氣味的能力,以年輕果蠅的效果較佳;顏色訓練方面,果蠅亦可分辨記憶顏色;密集學習方面,適當學習次數內,有助於增加果蠅的記憶能力,但過度的學習刺激會降低學習效果。並且,我們選顏色訓練中記憶較佳的一組進行迷宮實驗,經三次的岔路選擇,選出對顏色記憶最佳的果蠅,希望能探討訓練過的果蠅子代能否有較優良的記憶。至於記憶時間方面,一次氣味學習,果蠅在四分鐘內皆有記憶,且年輕果蠅記憶效果較強,達六分鐘;另外,多次氣味學習,果蠅於第四次訓練效果最佳,且記憶能力可達十二分鐘。希望藉本實驗報告,以期更瞭解果蠅學習與記憶的資料。
步步為營
Two soldiers walk on a checkerboard. They can only walk one step once a time and two directions, front and left, are decided randomly. The gunshot is the column and row where a soldier is located, and one will die if he enters the gunshot area of the other. To treat the probability of winning, we first study the cases of 1×n, 2×n, 3×n, and 4×n rectangles iterately. Then we establish a general form of the probability of winning in a general n×k rectangle by using recurrence technique and generating function, respectively. Finally, we extend to the general n×m×k cuboid case to obtain the first soldier’s probability of winning.在一個長方形的棋盤中,兩士兵行走,每一次只走一步,而且上和左兩個方向是隨機的,射程範圍是所在的此行和此列,而進入他人射程範圍則死亡。探討其獲勝機率,從1×n 、2×n、3×n、4×n 矩形的情形逐步研究,並分別運用遞迴式的技巧及生成函數,導出 n×k 矩形中先走士兵獲勝機率的一般式。更進一步地,我們也獲得了n×m×k 立體空間先走士兵的獲勝機率。
螺旋狀剝皮對樹木影響之初步研究
本研究的目的在於探討螺旋狀剝皮對植物生存以及芭樂果實的影響。實驗的設計是將選擇的植株或其枝幹分成四組,分別施予環狀剝皮、螺旋狀剝皮一圈、螺旋狀剝皮三圈及不剝皮等處理。 研究結果顯示,螺旋狀剝皮不會導致植株死亡,且於處理部位下方會長出新的枝葉。芭樂果實經100 天的生長之後,不剝皮處理之枝幹長出的芭樂重量都在 300g 以下,而螺旋狀剝皮一圈之枝幹長出的芭樂有重達300-400g(5%)及 400-500g(5%),最重的達 490g;螺旋狀剝皮三圈之枝幹長出的芭樂也有重達 300-400g(占 7.7%)。此外,與不剝皮處理者比較之,螺旋狀剝皮也有助於高甜度芭樂比例的提升。 本研究成果若能成功應用在其他果樹上,有助於提高果農產收的經濟價值。 The purpose of our study is to examine spiral bark-stripping’s effects on trees, and observe what will happen with this treatment, especially in the survival of trees and fruit of Guava. The experimental design is as below. First, we divided tree samples or branches into 4 groups randomly, and then treated each group differently with girdling, spiral bark-stripping a circle, spiral bark-stripping 3 circles, or non-stripping on the trunks or branches. As a result, spiral bark-stripping did not cause death of trees. Instead, new green leaves grew below treated area. After 100 days of growth, the fruit of Guava treated with non-stripping weighed below 300 grams, while some fruit weighing above 300-400 grams(5%) and 400-500 grams(5%) grew on those trees treated with spiral bark-stripping a circle, with the heaviest of 490 grams. Besides, there are some fruit weighing 300-400 grams(7.7%) growing on those trees treated with piral bark-stripping 3 circles. The result shows that spiral bark-stripping, compared to non-stripping, promoted the proportion of high-sugar fruit. This study provides a possible way to increase the economic value of fruit harvest if applied to other kinds of fruit trees.