PLDは、カナダのプロテインエンジニアリング研究委員長を務めています。この研究は、カナダ保健研究所からPLDへの助成金によって資金提供されました。また、日本学術振興会(JSPS)(第23310171)と日本バイオ志向技術研究振興機構(BRAIN)の科学研究助成も支援しました。クリス・マーシャル博士とマイク・カイパー博士のFPAに先駆けての研究に感謝しています。また、津田栄博士が本研究の一部に施設を提供し、蛍光灯の励起フィルターや発光フィルターを設置してくれたローリー・グラハム博士にも感謝しています。

1. 単一の氷の結晶を成長
<ol><li>エチレングリコール冷却浴に収まり、浮遊できるきれいな金属鍋(直径15cm、高さ4.5cm)を取ります。</li>
	<li>ポリ塩化ビニル(PVC)円筒形金型(直径4.5cm、高さ3〜4cm、厚さ4mm)をパイプから鋸で準備します。<ol>
<li>片方(図1A)のノッチ(幅1mm、高さ2mm)を切ります。</li>
		<li>鍋に快適に収まる金型を多く準備します(図1B)。 注: 研究は、ポリビニルアルコール(PVA)が氷の核化22に影響を与えることができることを示しました。しかし、私たちのオープンモールドPVCシステムでは、非定型の氷形成の問題に遭遇していません。</li>
	</ol>
</li>
	<li>各金型の底面リングに真空グリースの光フィルムを塗布し、ノッチを切り取った表面です。このグリースを塗ったノッチサーフェスを、フライパンの中央から離れた位置に向けたノッチを持つ金属鍋にシールします。油を塗ったり、グリスでノッチを妨げないように注意してください。</li>
	<li>0.22 μmを濾過・脱気/脱イオン水を鍋の中心に加え、金型の外側に加え、ノッチを通してゆっくりと金型に入るようにします。気泡を導入しないように注意してください。水層は約5mmの深さでなければなりません。</li>
	<li>鍋を温度制御エチレングリコール浴槽に入れ、-0.5°Cに冷却します。 鍋は完全にレベルでなければなりません。必要に応じて、鍋の側面にバラストウェイトを追加します。</li>
	<li>鍋と水が-0.5 °Cに達した後、鍋の真ん中に小さな氷を、型の外側に加えます。<ol>
<li>これは鍋を横切って型に過冷却水の氷の成長を有核します。各金型の底部にある小さなノッチは、1つの氷の結晶だけが伝播し、各金型に単一の氷の結晶をもたらします。</li>
		<li>一晩インキュベートして氷の層を形成する。</li>
	</ol>
</li>
	<li>次の3日間で、1日1回、各金型に4°C脱気/脱イオン水の13mlを加え、1日目に-0.8°C、2日目に-1.1°C、3日目に-1.5°Cに添加した後、エチレングリコール浴の温度を低下させます。<ol>
<li>これらの温度で一晩インキュベートします。</li>
		<li>4日目までに、金型は完全に氷で満たされるべきです。</li>
	</ol>
</li>
	<li>鍋から金型を引き出し、氷の結晶を金型から押し出し、計量ボートなどのきれいな表面に約1時間-20°Cの冷凍庫で保管してから取り扱います。</li>
	<li>多くの小さな単氷結晶を調製するのではなく、数リットルの体積の大きな単一氷結晶を、ナイト23で説明したように一定温度インキュベーターで調製することができる。大きな氷の結晶は、-15〜-20°Cの冷凍庫で覆われておけば1年以上保存することができます。単結晶の一部は、必要に応じて鋸で氷ブロックから切断することができます。</li>
</ol>2. 氷結晶の特異点と配向の決定
<ol><li>金型から排出された氷が、2つの交差したポラロイドの間のフリーザールームで観察することによって単結晶であるかどうかを判断する(図1D)。<ol>
<li>氷の結晶が単一の場合、亀裂や不連続性は見られないので、氷の結晶の中で光の方向が変化してはいけません。 注: 冷凍室が利用できない場合は、必要なすべての手順で冷たい部屋を使用することができ、迅速に作業し、氷を控えめに扱う際に注意が必要です。</li>
	</ol>
</li>
	<li>氷の複屈折のために 、c軸の向きを同時に決定することがあります。次の情報を使用して、向きを決定します。<ol>
<li>c軸が入射光と正確に平行である場合、理論的には、交差したポラロイドを通過する光はありません。入射光がc軸と平行からわずかにタイトルが付けられている場合、交差したポラロイド間で回転すると、均一な多色スペクトルの光が結晶を透過します。この均一な透過率は、そのc軸24に沿った氷Ihの光学的不活性から生じる。氷の結晶の基底面は、c軸に垂直である。</li>
		<li>c軸が入射光と平行から離れ、氷の結晶が交差したポラロイド間で回転すると、透過光は結晶の90°回転ごとに0-100%の透過率の間で交互になります。</li>
		<li>最も一般的には 、c軸は円筒状の氷の結晶の円形平面に垂直になります。</li>
	</ol>
</li>
	<li>氷の結晶をアルミニウム箔でしっかりと包み、小さな穴をホイルを通して基底面の氷に突き刺し(c軸に垂直)、20分間真空下に置くことによって行われる氷の穴25によって軸の向きを決定する。<ol>
<li>この処理は、基底面に六角形対称のエッチングを生成し、-axesが6面の星の頂点を通って走る(図2A)。</li>
		<li>必要であれば、氷結晶は、それぞれ冷たい指に垂直な一次または二次プリズム面とそれを取り付けるために六角形の一方の側に平行または垂直の鋸で切断することができる(図3)。</li>
	</ol>
</li>
</ol>3. 蛍光標識不凍タンパク質の単一氷結晶への吸着
<ol><li>冷たい指 (図1C)に、最初にキャビティを結晶の上部にボーリングして、単一の氷の結晶を取り付けます。これを行うには、わずかに異なる直径の2つのアルミニウム棒で氷を交互に融解し、冷たい指の直径に似ているが、冷たい指が合うことができる空洞を形成する。</li>
	<li>冷たい指を-0.5°Cに冷却し、氷の空洞に入れ、氷の結晶が金属に凍るまで所定の位置に保持します(図2B)。水晶を指に取り付ける際は、指からロッドへの熱の効率的な伝達を妨げるため、気泡を避けてください。</li>
	<li>氷晶の直径の約2倍の半球状のカップを、濾過された脱イオン水または緩衝液で満たし、約4°Cに冷却する。 冷たい指に結合した氷の結晶をカップに浸し、氷の結晶の上部が液体層とほぼ同じレベルで、氷がカップの壁に触れていないような余分な水または緩衝液を取り除きます。<ol>
<li>カップを断熱材で覆い、温度を-5 °Cに下げます。</li>
		<li>氷の結晶が半球になるまで約1時間待ち、約20分ごとにその状態を確認します(図2C)。</li>
		<li>氷は氷の結晶を溶かして成長させることによって半球形のカップの形を取りますが、カップの壁に触れて成長してはいけません。壁と半球の間に少なくとも1cmの隙間があり、冷たい指が氷から突き出てはいけない。</li>
	</ol>
</li>
	<li>氷の結晶からカップを取り出し、蛍光タンパク質溶液を25〜30mlの最終体積と所望の分析濃度に加え、カップ中の全液量を変えない所見に注意してください。典型的な AFP 濃度は 0.1 mg/ml です。<ol>
<li>氷の結晶の上部が液体と同じレベルにあり、氷の結晶がカップの壁に触れていないように、カップに氷の結晶を再結合します(図2D)。</li>
		<li>冷たい指の温度を-8°Cに落とし、タンパク質溶液を氷晶中に2〜3時間凍結させ、溶液を頻繁に攪拌する。タンパク質溶液から形成された氷は、氷の成長を止める前に少なくとも5mmでなければなりません。</li>
	</ol>
</li>
	<li>冷たい指に取り付けながら、カップから氷の結晶を取り除きます。冷たい指を通して冷媒を0°Cのすぐ上に温めて後者から氷を取り外し、氷の結晶が溶けるまで待ちます。</li>
	<li>水晶平らな面を計量皿などのきれいな表面に下ろし、新たに氷を形成しないように注意し、手渡す前に少なくとも20分間-20°Cで保存してください。</li>
</ol>4. 不凍タンパク質結合氷の平面の可視化
<ol><li>蛍光の可視化は、暗くなった冷凍庫または冷たい部屋で行われ、氷結晶を波長特異的な励起フィルタ付きランプの下に置き、蛍光標識とカメラエミッションフィルタを励起して他の非特異的光を遮断する。パターンに基づいて、AMP によって結合された氷面を推定することができます(図4)。</li>
	<li>波長固有のライトが使用できない場合は、代わりに UV ライト ボックスを使用できます。</li>
	<li>従来の氷のエッチングは、氷半球が-20°Cで少なくとも3時間昇華するようにすることで、氷表面に残留タンパク質粉末が見えるようにすることによっても行うことができる(図5)。</li>
	<li>ステップ 2.3 を繰り返して、完成した氷半球の -軸の方向を決定できます。</li>
</ol>

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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+glycopeptides+and+peptides+in+inhibition+of+crystallization+of+water+in+polar+fishes.">Role of glycopeptides and peptides in inhibition of crystallization of water in polar fishes.</a> Philos. T Roy. Soc. B. 304 (1121), 575-588 (1984).</li><li>Pertaya, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+microscopy+evidence+for+quasi-permanent+attachment+of+antifreeze+proteins+to+ice+surfaces.">Fluorescence microscopy evidence for quasi-permanent attachment of antifreeze proteins to ice surfaces.</a> Biophys. J. 92 (10), 3663-3673 (2007).</li><li>Kondo, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ice-binding+site+of+snow+mold+fungus+antifreeze+protein+deviates+from+structural+regularity+and+high+conservation.">Ice-binding site of snow mold fungus antifreeze protein deviates from structural regularity and high conservation.</a> Proc. Natl. Acad. Sci. U.S.A. 109 (24), 9360-9365 (2012).</li><li>Mok, Y. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+basis+for+the+superior+activity+of+the+large+isoform+of+snow+flea+antifreeze+protein.">Structural basis for the superior activity of the large isoform of snow flea antifreeze protein.</a> Biochemistry. 49 (11), 2593-2603 (2010).</li><li>Takamichi, M., Nishimiya, Y., Miura, A., Tsuda, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fully+active+qae+isoform+confers+thermal+hysteresis+activity+on+a+defective+sp+isoform+of+type+iii+antifreeze+protein.">Fully active qae isoform confers thermal hysteresis activity on a defective sp isoform of type iii antifreeze protein.</a> FEBS J. 276 (5), 1471-1479 (2009).</li><li>Bar-Dolev, M., Celik, Y., Wettlaufer, J. S., Davies, P. L., Braslavsky, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+insights+into+ice+growth+and+melting+modifications+by+antifreeze+proteins.">New insights into ice growth and melting modifications by antifreeze proteins.</a> J. R. Soc. Interface. 9 (77), 3249-3259 (2012).</li><li>Celik, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+experiments+reveal+that+antifreeze+proteins+bound+to+ice+crystals+suffice+to+prevent+their+growth.">Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth.</a> Proc. Natl. Acad. Sci. U.S.A. 110 (4), 1309-1314 (2013).</li><li>Garnham, C. P., Campbell, R. L., Walker, V. K., Davies, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+dimeric+beta-helical+model+of+an+ice+nucleation+protein+with+bridged+active+sites.">Novel dimeric beta-helical model of an ice nucleation protein with bridged active sites.</a> BMC Struct. Biol. 11, (2011).</li></ol>

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AFP結合した氷面の決定のためのチャールズ・ナイトによる氷エッチング法の開発は、AfPによる氷結合のメカニズムに関する研究を大幅に進めた。AMPの構造はX線結晶学26,27 によって解決できるのに対し、AFPが結合した氷上の相補表面を推測する明白な方法はなかった。冬ヒラメからのタイプI AFPが最初に特徴づけられたとき、それは氷28の主要プリズム面に結合すると仮定され?...

不凍タンパク質(AMP)の生産は、氷を含んだ環境に生息する一部の生物の重要な生存メカニズムです。最近まで、AMPの唯一の機能は、循環を妨げ、組織損傷、浸透ストレスを引き起こす内部氷結晶の成長を予防または遅くすることであると考えられていた。魚のようないかなる程度の凍結を許容できない生物は、氷晶成長を完全に阻害するAMPを発現する1。草などの他の人は、凍結耐性であり、それらの組織中の大きな氷の結晶の形成を減少させる氷再結晶を阻害するAMPを発現する2。低温での膜の安定化は、AfPS3に対して提案されたもう一つの機能です。最近、氷に覆われた汽水湖4から南極細菌マリノモナスプリモレンシスのAFPに新しい役割が示唆された。このAFPは、酸素と栄養素へのより良いアクセスのために細菌を氷に付着すると考えられているはるかに大きなアフェシンタンパク質5の一部である6。他の微生物は、彼らが住んでいる氷の構造を変更する可能性があるAMPを分泌することが知られています7.
AMPは、いくつかの魚、昆虫、植物、藻類、細菌、珪藻類、および真菌で発見されています。彼らは様々な機会に異なる前駆者からの進化と一致する著しく発散的な配列と構造を有する。しかし、それらはすべて氷に結合し、吸着阻害メカニズム8によってその成長を阻害する。AfP はそれぞれ、氷結合部位(IBS)として機能する特定のサーフェスを持っています。これらは、典型的には、9-11の表面残基の部位特異的突然変異誘発によって同定された。IBSは、氷の特定の平面に一致する氷のようなパターンで水分子を配置するために仮説されています。したがって、AFPは5,12に結合する前にリガンドを形成する。氷面はミラーインデックスによって定義することができ、異なるAMPは異なる平面に結合することができます。したがって、冬のヒラメからのタイプI AFPは20-21錐形の平面13に結合し、III型AFPは複合氷結合表面11,14を使用して一次プリズムとピラミッド面の両方を結合し、スプルース・ブドワームAFPは多動性AFPである一次面と基礎面15,16の両方に同時に結合する。 MPAFPなどの他の多動性AfPは、単一の氷結晶半球5,17の完全なカバレッジによって示されるように、複数の氷面に結合する。これは、多動性AMPが基底面を結合する能力と他の平面が、適度に活動的なAMP18に対する10倍の高い活性を占める可能性があると仮定されている。多動性AMPの効率は十分に文書化されていますが、複数の氷面に結合する能力はまだ理解されていません。
AFPに結合した氷面を決定するための元の方法は、チャールズナイト13,19によって開発されました。この方法では、マクロ的な単一の氷の結晶を中空の金属棒(冷指)に取り付け、脱気水で満たされた半球カップに水没させることによって半球に形成される。その後、半球はAFPsの希薄溶液に沈め、氷の層はAFP溶液から氷結晶半球に数時間にわたって成長し、冷たい指を循環するエチレングリコールの温度によって制御される。氷の結晶を溶液から取り出し、冷たい指から取り外し、-10〜-15°Cの冷凍室に入れた。表面を鋭い刃で削り取って不凍タンパク質溶液の凍結表面膜を除去し、氷晶を少なくとも3時間昇華させた。昇華後、AFPによって結合された氷面は、残留タンパク質に由来する白色のエッチングパターンと見なすことができる。氷半球は、そのc軸と-軸に向けて、氷の基底面およびプリズム平面を見つけ、エッチングされたパッチのミラー指数を決定することができます。
ここでは、AFP結合した氷の平面を決定するための元の方法の改変について述べているが、我々は蛍光ベースの氷面親和性(FIPA)11と呼ぶ方法である。このAFPは、緑色蛍光タンパク質(GFP)11、16、17、20などのキメラタグで蛍光標識されるか、またはAFP5,21に共有結合した蛍光色素を有する。蛍光標識されたAFPは、単一の氷結晶に吸着され、元の氷エッチング実験と同じ実験手順を使用して生い茂る。成長する氷半球に対するAFP結合の程度は、紫外線(UV)ランプを使用して実験全体を通して監視することができる。実験が完了した後、半球は冷たい指から直接取り除かれ、昇華することなく画像化することができます。しかし、必要に応じて、半球を昇合したままにして、伝統的な氷のエッチングを視覚化することができます。FIPAの方法論に導入された変更は、従来の氷エッチングプロトコルを数時間短縮する。さらに、それぞれ異なる蛍光標識を持つ複数のAfPsを同時にイメージングして、AFP結合した氷面の重複するパターンを視覚化する可能性があります。

<table border="0" cellpadding="0" cellspacing="0" width="605">
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			<td height="42" style="height:42px;width:177px;">NESLAB RTE Refrigerating Bath/Circulators</td>
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			<td height="48" style="height:48px;width:177px;">Ethylene glycol, Premixed Antifreeze/Coolant</td>
			<td style="width:95px;">Certified</td>
			<td style="width:145px;">29-3037-0</td>
			<td style="width:189px;">Common automotive antifreeze</td>
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			<td height="65" style="height:65px;width:177px;">Cold finger</td>
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			<td height="84" style="height:84px;width:177px;">High Dual Output Lighting System</td>
			<td style="width:95px;">Lightools Research</td>
			<td style="width:145px;">LT-99D2, Illumatools DLS 120 volts AC, LT-9470FX, LT-9549FX</td>
			<td style="width:189px;">Additional and custom excitation filters can be purchased from Lightools Research</td>
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			<td height="40" rowspan="2" style="height:40px;width:177px;">Camera</td>
			<td rowspan="2" style="width:95px;">Canon</td>
			<td rowspan="2" style="width:145px;">EOS 50D</td>
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			<td height="79" style="height:79px;width:177px;">Emission Filters</td>
			<td style="width:95px;">Lightools Research</td>
			<td style="width:145px;">LT-9EFPVG, LT-9GFPVG, LT-9RFPVG</td>
			<td style="width:189px;">Filter ring adapter may be required to fit filter onto camera lens</td>
		</tr>
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</table>

determining the ice-binding planes of antifreeze proteins by fluorescence-based ice plane affinity

不凍タンパク質(AFP)は、内部の氷の成長を防ぐか、または遅くするために、様々な冷たい硬い生物で発現されています。AFPは、氷結合表面を通して特定の氷の平面に結合する。蛍光ベースの氷面アフィニティー(FIPA)解析は、AfPが結合する氷面を決定するために使用される修正技術です。FIPAは、AFP結合の氷面を決定するための元の氷エッチング方法に基づいています。それは短い実験の時間でより明確なイメージを作り出す。FIPA分析では、AfPSはキメラタグまたは共有色素で蛍光標識され、その後ゆっくりと巨視的な単氷結晶に組み込まれ、半球に予知され 、a軸 と c軸を決定するように配向されています。AFPバウンド氷半球はUV光の下で画像化され、非特異光を遮断するフィルターを使用してAFPバウンド平面を視覚化する。AfPsの蛍光標識により、AFPの氷への吸着をリアルタイムに監視できます。ラベルは、AMP がバインドする平面に影響を与えないことが判明しました。FIPA分析では、同じ単氷結晶上で複数の異なるタグ付きAFPを結合し、結合面を区別するオプションも導入されています。FIPAのこれらのアプリケーションは、AAFPがその成長を止めるために氷に結合する方法と、多くのAFP生産生物が複数のAFPアイソフォームを発現する理由についての理解を深めるのに役立っています。

単一の氷の結晶の準備および取付けは、エラーが最も一般的に行われるFIPA手順の2つのステップである。プロトコルセクションのステップ2.1で概説したように、調製された氷結晶が単一であるかどうかを調べることによって、交差したポラロイド(図1D)を調べることによって決定する。多結晶性の氷結晶がFIPA分析に使用される場合、結果は、コヒーレント結合パターンなしで半球?...

Watch this Scientific Journal Video about Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity at JoVE.com

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

不凍タンパク質(AFP)は、氷の特定の平面に結合して、氷の成長を防ぐか、または遅くします。蛍光ベースの氷面親和性(FIPA)分析は、AFP結合した氷面の決定のためのオリジナルの氷エッチング法の改変である。AFPは蛍光標識され、巨視的な単氷結晶に組み込まれ、UV光下で可視化されます。

蛍光ベースの氷面アフィニティーによる不凍タンパク質の氷結合平面の決定

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice ...

determining-ice-binding-planes-antifreeze-proteins-fluorescence-based

Research

JoVE Journal

Chemistry

8.9K ビュー.  Queen's University. 不凍タンパク質(AFP)は、氷の特定の平面に結合して、氷の成長を防ぐか、または遅くします。蛍光ベースの氷面親和性(FIPA)分析は、AFP結合した氷面の決定のためのオリジナルの氷エッチング法の改変である。AFPは蛍光標識され、巨視的な単氷結晶に組み込まれ、UV光下で可視化されます。

ビデオ: Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

LabVIEW-operated Novel Nanoliter Osmometer for Ice Binding Protein Investigations

Ice-binding proteins (IBPs), including antifreeze proteins, ice structuring proteins, thermal hysteresis proteins, and ice recrystallization inhibition proteins, are found in cold-adapted organisms and protect them from freeze injuries by interacting with ice crystals. IBPs are found in a variety of organism, including fish1, plants2, 3, arthropods4, 5, fungi6, and bacteria7. IBPs adsorb to the surfaces of ice crystals and prevent water molecules from joining the ice lattice at the IBP adsorption location. Ice that grows on the crystal surface between the adsorbed IBPs develops a high curvature that lowers the temperature at which the ice crystals grow, a phenomenon referred to as the Gibbs-Thomson effect. This depression creates a gap (thermal hysteresis, TH) between the melting point and the nonequilibrium freezing point, within which ice growth is arrested8-10, see Figure 1. One of the main tools used in IBP research is the nanoliter osmometer, which facilitates measurements of the TH activities of IBP solutions. Nanoliter osmometers, such as the Clifton instrument (Clifton Technical Physics, Hartford, NY,) and Otago instrument (Otago Osmometers, Dunedin, New Zealand), were designed to measure the osmolarity of a solution by measuring the melting point depression of droplets with nanoliter volumes. These devices were used to measure the osmolarities of biological samples, such as tears11, and were found to be useful in IBP research. Manual control over these nanoliter osmometers limited the experimental possibilities. Temperature rate changes could not be controlled reliably, the temperature range of the Clifton instrument was limited to 4,000 mOsmol (about -7.5 &deg;C), and temperature recordings as a function of time were not an available option for these instruments.
We designed a custom-made computer-controlled nanoliter osmometer system using a LabVIEW platform (National Instruments). The cold stage, described previously9, 10, contains a metal block through which water circulates, thereby functioning as a heat sink, see Figure 2. Attached to this block are thermoelectric coolers that may be driven using a commercial temperature controller that can be controlled via LabVIEW modules, see Figure 3. Further details are provided below. The major advantage of this system is its sensitive temperature control, see Figure 4. Automated temperature control permits the coordination of a fixed temperature ramp with a video microscopy output containing additional experimental details.
To study the time dependence of the TH activity, we tested a 58 kDa hyperactive IBP from the Antarctic bacterium Marinomonas primoryensis (MpIBP)12. This protein was tagged with enhanced green fluorescence proteins (eGFP) in a construct developed by Peter Davies' group (Queens University)10. We showed that the temperature change profile affected the TH activity. Excellent control over the temperature profile in these experiments significantly improved the TH measurements. The nanoliter osmometer additionally allowed us to test the recrystallization inhibition of IBPs5, 13. In general, recrystallization is a phenomenon in which large crystals grow larger at the expense of small crystals. IBPs efficiently inhibit recrystallization, even at low concentrations14, 15. We used our LabVIEW-controlled osmometer to quantitatively follow the recrystallization of ice and to enforce a constant ice fraction using simultaneous real-time video analysis of the images and temperature feedback from the sample chamber13. The real-time calculations offer additional control options during an experimental procedure. A stage for an inverted microscope was developed to accommodate temperature-controlled microfluidic devices, which will be described elsewhere16.
The Cold Stage System
The cold stage assembly (Figure 2) consists of a set of thermoelectric coolers that cool a copper plate. Heat is removed from the stage by flowing cold water through a closed compartment under the thermoelectric coolers. A 4 mm diameter hole in the middle of the copper plate serves as a viewing window. A 1 mm diameter in-plane hole was drilled to fit the thermistor. A custom-made copper disc (7 mm in diameter) with several holes (500 &mu;m in diameter) was placed on the copper plate and aligned with the viewing window. Air was pumped at a flow rate of 35 ml/sec and dried using Drierite (W.A. Hammond). The dry air was used to ensure a dry environment at the cooling stage. The stage was connected via a 9 pin connection outlet to a temperature controller (Model 3040 or 3150, Newport Corporation, Irvine, California, US). The temperature controller was connected via a cable to a computer GPIB-PCI card (National instruments, Austin, Texas, USA).

Ice binding proteins (IBPs), also known as antifreeze proteins, inhibit ice growth and are a promising additive for use in the cryopreservation of tissues. The main tool used to investigate IBPs is the nanoliter osmometer. We developed a home-designed cooling stage mounted on an optical microscope and controlled using a custom-built LabVIEW routine. The nanoliter osmometer described here manipulated the sample temperature in an ultra-sensitive manner.

アイス結合タンパク質の調査用のLabVIEWオペ新規ナノリッター浸透圧計

Ice-binding proteins (IBPs), including antifreeze proteins, ice structuring proteins, thermal hysteresis proteins, and ice recrystallization inhibition ...

化学

Methods to Identify the NMR Resonances of the 13C-Dimethyl N-terminal Amine on Reductively Methylated Proteins

Nuclear magnetic resonance (NMR) spectroscopy is a proven technique for protein structure and dynamic studies. To study proteins with NMR, stable magnetic isotopes are typically incorporated metabolically to improve the sensitivity and allow for sequential resonance assignment. Reductive 13C-methylation is an alternative labeling method for proteins that are not amenable to bacterial host over-expression, the most common method of isotope incorporation. Reductive 13C-methylation is a chemical reaction performed under mild conditions that modifies a protein&#39;s primary amino groups (lysine &#949;-amino groups and the N-terminal &#945;-amino group) to 13C-dimethylamino groups. The structure and function of most proteins are not altered by the modification, making it a viable alternative to metabolic labeling. Because reductive 13C-methylation adds sparse, isotopic labels, traditional methods of assigning the NMR signals are not applicable. An alternative assignment method using mass spectrometry (MS) to aid in the assignment of protein 13C-dimethylamine NMR signals has been developed. The method relies on partial and different amounts of 13C-labeling at each primary amino group. One limitation of the method arises when the protein&#39;s N-terminal residue is a lysine because the &#945;- and &#949;-dimethylamino groups of Lys1 cannot be individually measured with MS. To circumvent this limitation, two methods are described to identify the NMR resonance of the 13C-dimethylamines associated with both the N-terminal &#945;-amine and the side chain &#949;-amine. The NMR signals of the N-terminal &#945;-dimethylamine and the side chain &#949;-dimethylamine of hen egg white lysozyme, Lys1, are identified in 1H-13C heteronuclear single-quantum coherence spectra.

Methods to Identify the NMR Resonances of the 13C-Dimethyl N-terminal Amine on Reductively Methylated Proteins

Two methods for assigning the &#945;- and &#949;-dimethylamine nuclear magnetic resonance signals of a reductively 13C-methylated N-terminal lysine are described. One method utilizes the pH-induced selectivity of the reductive methylation reaction, and the other uses aminopeptidase to selectively remove the N-terminal lysine.

Nuclear magnetic resonance (NMR) spectroscopy is a proven technique for protein structure and dynamic studies. To study proteins with NMR, stable magnetic ...

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

短いペプチドの自己組織化によって順序付け生体分子構造の形成

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Submillisecond Conformational Changes in Proteins Resolved by Photothermal Beam Deflection

Photothermal beam deflection together with photo-acoustic calorimetry and thermal grating belongs to the family of photothermal methods that monitor the time-profile volume and enthalpy changes of light induced conformational changes in proteins on microsecond to millisecond time-scales that are not accessible using traditional stop-flow instruments. In addition, since overall changes in volume and/or enthalpy are probed, these techniques can be applied to proteins and other biomacromolecules that lack a fluorophore and or a chromophore label. To monitor dynamics and energetics of structural changes associated with Ca2+ binding to calcium transducers, such neuronal calcium sensors, a caged calcium compound, DM-nitrophen, is employed to photo-trigger a fast (&#964; &#60; 20 &#956;sec) increase in free calcium concentration and the associated volume and enthalpy changes are probed using photothermal beam deflection technique.

Here we report an application of the photothermal beam deflection technique in combination with a caged calcium compound, DM-nitrophen, to monitor microsecond and millisecond dynamics and energetics of structural changes associated with the calcium association to a neuronal calcium sensor, Downstream Regulatory Element Antagonist Modulator.

光熱ビーム偏向によって分離したタンパク質におけるミリ秒以下構造変化

Photothermal beam deflection together with photo-acoustic calorimetry and thermal grating belongs to the family of photothermal methods that monitor the ...

Fluorescence-based Monitoring of PAD4 Activity via a Pro-fluorescence Substrate Analog

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein substrates. The histone tails represent one of the most heavily modified stretches within all human proteins. Peptidyl-arginine deiminase 4 (PAD4) has been shown to convert arginine residues into the non-genetically encoded citrulline residue. Few assays described to date have been operationally facile with satisfactory sensitivity. Thus, the lack of adequate assays has likely contributed to the absence of potent non-covalent PAD4 inhibitors. Herein a novel fluorescence-based assay that allows for the monitoring of PAD4 activity is described. A pro-fluorescent substrate analog was designed to link PAD4 enzymatic activity to fluorescence liberation upon the addition of the protease trypsin. It was shown that the assay is compatible with high-throughput screening conditions and has a strong signal-to-noise ratio. Furthermore, the assay can also be performed with crude cell lysates containing over-expressed PAD4.

PAD4 is an enzyme responsible for the conversion of peptidyl-arginine to peptidyl-citrulline. Dysregulation of PAD4 has been implicated in a number of human diseases. A facile and high-throughput compatible fluorescence based PAD4 assay is described.

プロ蛍光基質アナログを経由してPAD4活性の蛍光ベースの監視

Post-translational modifications may lead to altered protein functional states by increasing the covalent variations on the side chains of many protein ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

合成タンパク質の最適化：中間物挿入依存関係の同定構造的インジケートおよび/または機能的に連結された残基

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum Interface (SALVI) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The fibronectin protein film was immobilized on the silicon nitride (SiN) membrane that forms the SALVI detection area. During ToF-SIMS analysis, three modes of analysis were conducted including high spatial resolution mass spectrometry, two-dimensional (2D) imaging, and depth profiling. Mass spectra were acquired in both positive and negative modes. Deionized water was also analyzed as a reference sample. Our results show that the fibronectin film in water has more distinct and stronger water cluster peaks compared to water alone. Characteristic peaks of amino acid fragments are also observable in the hydrated protein ToF-SIMS spectra. These results illustrate that protein molecule adsorption on a surface can be studied dynamically using SALVI and ToF-SIMS in the liquid environment for the first time.

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work presents a protocol for liquid handling and sample introduction to a microchannel for in situ time-of-flight secondary ion mass spectrometry analysis of protein biomolecules in an aqueous solution.

サルヴィとTOF-SIMSによる水中で水和タンパク質のその場キャラクタリゼーションで

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Photoredox触媒を用いた可視光媒介分散重合によるワームのようなミセルの簡便な合成

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

A protocol to avoid the oxidation of metallic substrates during sample transfer from an inhibited acidic solution to an X-ray photoelectron spectrometer is presented.

XPSで腐食防止剤/金属界面の化学組成を決定する：最小化後のイマージョン酸化

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, ...

An HS-MRM Assay for the Quantification of Host-cell Proteins in Protein Biopharmaceuticals by Liquid Chromatography Ion Mobility QTOF Mass Spectrometry

The analysis of low-level (1-100 ppm) protein impurities (e.g., host-cell proteins (HCPs)) in protein biotherapeutics is a challenging assay requiring high sensitivity and a wide dynamic range. Mass spectrometry-based quantification assays for proteins typically involve protein digestion followed by the selective reaction monitoring/multiple reaction monitoring (SRM/MRM) quantification of peptides using a low-resolution (Rs ~1,000) tandem quadrupole mass spectrometer. One of the limitations of this approach is the interference phenomenon observed when the peptide of interest has the "same" precursor and fragment mass (in terms of m/z values) as other co-eluting peptides present in the sample (within a 1-Da window). To avoid this phenomenon, we propose an alternative mass spectrometric approach, a high selectivity (HS) MRM assay that combines the ion mobility separation of peptide precursors with the high-resolution (Rs ~30,000) MS detection of peptide fragments. We explored the capabilities of this approach to quantify low-abundance peptide standards spiked in a monoclonal antibody (mAb) digest and demonstrated that it has the sensitivity and dynamic range (at least 3 orders of magnitude) typically achieved in HCP analysis. All six peptide standards were detected at concentrations as low as 0.1 nM (1 femtomole loaded on a 2.1-mm ID chromatographic column) in the presence of a high-abundance peptide background (2 &#181;g of a mAb digest loaded on-column). When considering the MW of rabbit phosphorylase (97.2 kDa), from which the spiked peptides were derived, the LOQ of this assay is lower than 50 ppm. Relative standard deviations (RSD) of peak areas (n = 4 replicates) were less than 15% across the entire concentration range investigated (0.1-100 nM or 1-1,000 ppm) in this study.

Here, we describe a chromatographic assay coupled with the ion mobility separation of peptide precursors followed by the high-resolution (~30,000) MS-detection of peptide fragments for the quantification of spiked peptide standards in a monoclonal antibody digest.

液体クロマトグラフィーによるイオン移動 QTOF 質量分析法によるタンパク質のバイオ医薬品の宿主細胞蛋白質の定量化のための HS MRM アッセイ

The analysis of low-level (1-100 ppm) protein impurities (e.g., host-cell proteins (HCPs)) in protein biotherapeutics is a challenging assay requiring ...