Name: how equilibrium binding constant affects binding
Uploaded: 2023-04-30T18:28:41.000Z
Duration: 2 min 18 s
Channel: JoVE

في الخلية،البروتينات تصطدم بجزيئات أخرى عشوائيًا مثل البروتينات الأخرى،الأحماض النووية و الجزىء الصغير الليجاند. إذا كان الربط غير محدد،فإن قليل من التفاعلات غير التساهمية بين الجزيئات ينتج عنها إقتران محدود. في حالة إرتباط ليجاند معين بالبروتين،فإنه يشكل تفاعلات غير تساهمية شاسعة على طول الأسطح التكميلية.مثل هذه المركبات تكون ثابتة،باقية مترابطة لفترة طويلة قبل التفكك قوة تفاعل الربط KB, قد ذٌكرت من حيث ثابت الاتزان يسمى أيضًا ثابت الربط أو ثابت الاقتران KBيمكن حسابه من نسبة تركيز مركب البروتين ليجاند مقسوم على تركيزات البروتين الغير مرتبط و الليجند الموجود في الإتزان. نظراًلعلاقتها بالتغير في الطاقة الحرة نتيجة الترابط, فإن KB الكبيرة تعني انخفاض كبير في دلتا جى يشيربذلك إلى انجذاب قوي بين البروتين والليجاند. اثنان من العمليات التنافسية تكون مهمة لربط البروتينات والليجاند.اقتران البروتين والليجاند لتكوين مركب معقد وفصل المركب لمواد متفاعلة. K on هو قياس ثابت إقتران عدد الترابطات الحادثة في الثانية بين بروتين والليجند الخاص به. يمكن استخدامه في حساب معدل ربط الليجاند بالبروتين في تركيز محدد.وعلى العكس من ذلك K off هو قياس عدد أحداث التفكك. يمكن استخدامه لحساب مدى السرعة التى يتفكك بها المركب عندما يكون معدل الاقتران يساوي معدل التفكك والاتزان قد حدث حيث, تركيزات النواتج من التفاعل و المواد المتفاعلة تبقى ثابتة. لذلك عند الاتزان،K on مضروب فى ناتج تركيزات الإتزان للبروتين والليجاند, يكون مساويا K off مضروبًا في تركيزات الاتزان لمركب البروتين الليجاند.إعادة ترتيب تلك الصيغة تظهر أن نسبة K off إلى K on تساوى KB عند الإتزان.

<ol>
	<li>بولارد ، توماس د. "دليل لمقايسات الربط البسيطة والغنية بالمعلومات". البيولوجيا الجزيئية للخلية 21 ، العدد 23 (2010): 4061-4067.</li>
	<li>هولم وإدوارد سي ومايك أ. تريفيثيك. "فحوصات ربط الترابط عند التوازن: التحقق من الصحة والتفسير". المجلة البريطانية لعلم الصيدلة 161 ، العدد 6 (2010): 1219-1237.</li>
	<li>ميدينا فرانكو ، خوسيه إل ، أوسكار مينديز لوسيو ، وكارينا مارتينيز مايورجا. "التفاعل بين النمذجة الجزيئية والمعلوماتية الكيميائية لتوصيف مشهد تفاعلات البروتين والليجند والبروتين والبروتين لاكتشاف الأدوية." في التطورات في كيمياء البروتين والبيولوجيا الهيكلية، المجلد 96 ، ص 1-37. مطبعة أكاديمية ، 2014.</li>
</ol>

ثابت ربط التوازن وقوة الربط

The Equilibrium Binding Constant and Binding Strength

<div style="direction: rtl;">

يحدد ثابت ترابط التوازن (K_b) قوة التفاعل بين البروتين والرابطة. يمكن حساب K_b على النحو التالي عندما يكون التفاعل في حالة توازن:

<img alt="Eq1" src="/files/ftp_upload/11513/Equation 1.png" style="text-align: center; max-width: 100%;">

حيث P وL هما البروتين غير المرتبط والربيطة، على التوالي، وPL هو مركب البروتين والرابطة.

نظرًا لأن كمية الروابط المرتبطة ترتبط أيضًا بمعدل ارتباط الروابط، يمكن للتجارب أيضًا تحديد K_b عن طريق فحص معدلات ارتباط البروتين بالروابط (k_on) والتفكك (k_off) باستخدام النسبة التالية:

<img alt="Eq1" src="/files/ftp_upload/11513/Equation 2.png" style="text-align: center; max-width: 100%;">

وبالتالي، يتم استخدام فئتين من فحوصات الارتباط لتحديد ثابت ربط التوازن - تلك التي تقيس تركيزات التوازن وتلك التي تقيس حركية التفاعل. وفي هذه الحالة، يجب أن يكون التفاعل في حالة توازن وقت القياس.

تعتمد طريقة تحديد تركيزات التوازن على الحساسية المطلوبة وسهولة اكتشاف الإشارة. لهذه الأسباب، يتم استخدام المقايسات الطيفية على نطاق واسع. في هذه التجارب، ينتج التفاعل تغيرًا في امتصاص المادة المتفاعلة أو المنتج عند طول موجي معين، يمكن اكتشافه بواسطة مقياس الطيف الضوئي للأشعة فوق البنفسجية. وبدلاً من ذلك، يمكن تمييز المادة المتفاعلة أو المنتج بمسبار فلورسنت أو قد تحتوي على فلوروفور جوهري. ثم، يمكن قياس تقدم التفاعل من التغير في الفلورسنت. يتم إجراء هذه الاختبارات عن طريق تغيير تركيزات أحد المواد المتفاعلة بينما تظل بقية التجربة ثابتة. يمكن بعد ذلك رسم النتائج بيانيًا وتحليلها باستخدام طرق مختلفة لتركيب المنحنى.

تتم أيضًا دراسة التفاعلات بين البروتينات والروابط باستخدام مجموعة متنوعة من التقنيات البيوكيميائية والطيفية. يساعد التحليل الهيكلي، باستخدام علم البلورات بالأشعة السينية والتحليل الطيفي للرنين المغناطيسي النووي، في التنبؤ بتفاعلات البروتين مع الروابط من خلال عمليات المحاكاة الجزيئية. تُستخدم الأساليب النظرية والحسابية، مثل دراسات الالتحام بالبروتينات، على نطاق واسع لتوصيف موضع وتفاعلات بروابط الجزيئات الصغيرة، بما في ذلك الأدوية المرشحة. يعد تصميم الأدوية بمساعدة الكمبيوتر بديلاً سريعًا ومنخفض التكلفة لتسريع وتيرة التجارب التقليدية واختبار الأخطاء للأدوية.

</div>

يحدد ثابت ربط التوازن (Kb) قوة تفاعل البروتين والترابط. يمكن حساب Kb على النحو التالي عندما يكون التفاعل عند ...

the-equilibrium-binding-constant-and-binding-strength

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Cell Biology

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Energy and Catalysis

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how equilibrium binding constant affects binding

The equilibrium binding constant describes how strongly two molecules bind at equilibrium. It is a useful way to compare binding strength in molecular interactions.

This topic focuses on how binding is measured and what the equilibrium binding constant means. A higher value indicates stronger binding, while a lower value indicates weaker binding. Understanding this constant helps explain how tightly molecules stay together under equilibrium conditions.

The page also connects the binding constant to real binding strength. It shows why this value matters when comparing different molecular pairs. For high school students, it provides a clear link between a chemistry concept and molecular behavior.

How Equilibrium Binding Constant Affects Binding

how-equilibrium-binding-constant-affects-binding

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The equilibrium binding constant describes how strongly two molecules bind at equilibrium. It is a useful way to compare binding strength in molecular interactions. This topic focuses on how binding is measured and what the equilibrium binding constant means. A higher value indicates stronger binding, while a lower value indicates weaker binding. Understanding this constant helps explain how tightly molecules stay together under equilibrium conditions. The page also connects the binding...

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Learn how the equilibrium binding constant reflects binding strength and why higher or lower values matter in molecular interactions at equilibrium.

How Equilibrium Binding Constant Affects Binding | JoVE K12

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How Equilibrium Binding Constant Affects Binding

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