70年代初,在Ca2+受體蛋白-鈣調(diào)素(CaM)的發(fā)現(xiàn)極其功能的研究基礎(chǔ)上提出Ca2+第二信使學(xué)說。細(xì)胞內(nèi)Ca2+的分布與轉(zhuǎn)移是形成Ca2+信號的基礎(chǔ),因此監(jiān)測Ca2+的動態(tài)變化是研究G蛋白偶聯(lián)受體(GPCR)有效刺激劑的重要手段。
AAT Bioquest 提供各種優(yōu)質(zhì)鈣離子檢測探針
1 Fluo8
Fluo-3和Fluo-4是常用的可見光激發(fā)的Ca2+指示劑,然而Fluo-3AM和Fluo-4 在體內(nèi)結(jié)合鈣離子后的熒光強(qiáng)度不高,需要比較苛刻的loading condition來加強(qiáng)熒光強(qiáng)度。AAT Bioquest?Fluo-8改善了二者的loading condition和熒光強(qiáng)度問題,比如Fluo-8只需要在室溫孵育,而Fluo-3和Fluo-4需要37度水浴,另外Fluo-8的熒光強(qiáng)度是Fluo-4的兩倍,是Fluo-3的4倍,另外Fluo-8依舊保持Fluo-3和Fluo-4的通道。
were incubated with 100 μL of 4 μM Fluo-3 AM, Fluo-4 AM and Fluo-8? AM (Cat# 21080) in HHBS at 37 °C for 1 hour. The cells were washed twice with 200 μL HHBS, then imaged
with a fluorescence microscope using FITC channel.
2 Calbryte? 系列
為什么Calbryte?系列能夠提高信噪比
首先Calbryte?系列被偶聯(lián)了乙酰氧基甲酯( acetoxymethyl ,AM),意義有二:一是利用AM的親酯性使得探針能夠順利進(jìn)入到細(xì)胞內(nèi);二是AM基團(tuán)保證了Calbryte? 熒光探針在沒有進(jìn)入細(xì)胞之前的非活性以及非熒光的特性,這樣就能減少非特異性信號,提高信噪比。
為什么Calbryte?系列熒光強(qiáng)度更強(qiáng)?
QY = Fluorescence Quantum Yield in the presence of 5 mM calcium citrate
這里跟大家提一個名詞,p-糖蛋白,p-glycoprotein 1 ,P-gp),在很多細(xì)胞里比如Hella,P-gp扮演著ATP依賴的離子泵將很多小分子泵出細(xì)胞外,當(dāng)然進(jìn)入細(xì)胞的鈣離子探針也免不了這種遭遇。這就導(dǎo)致被排到細(xì)胞外的探針會結(jié)合胞外的離子,造成背景值增高而胞內(nèi)的目的信號變?nèi)酰旁氡冉档汀S械臅尤氡鞘妫╬robenecid),一種通道抑制劑來減少這種泄露。但是這種物質(zhì)的添加并不理想,有報道TRPV2受體會被其激活而TAS2R 受體又會被其抑制,因此會給研究帶來不可預(yù)知的可變因素。
而Calbryte? dyes卻能夠通過平衡離子電量來擺脫窘境。進(jìn)入細(xì)胞后一旦被水解,便形成帶有大量負(fù)電荷的親水性分子大大降低了這種泄露。
Carbachol dose response was measured in CHO-M1 cells with Calbryte? 520 AM and Fluo-4 AM. CHO-M1 cells were seeded overnight at 50,000 cells/100 μL/well in a 96-well black wall/clear bottom costar plate. 100 μL of 10 μg/ml Calbryte? 520 AM in HH Buffer or 10 μg/ml Fluo-4 in HH Buffer was added and incubated for 45 minutes at 37 °C. Dye loading solution was then removed and replaced with 200 μL HH Buffer/well. Carbachol (50 μL/well) was added by FlexStation 3 to achieve the final indicated concentrations.
另外,AAT Bioquest? 提供無probenecid、無需洗滌的鈣離子檢測試劑盒,成為HTS的選擇。
Response of endogenous P2Y receptor to ATP in CHO-K cells. CHO-K cells were seeded overnight at 40,000 cells per 100 μL per well in a 96-well black wall/clear bottom costar plate. 100 μL of Calbryte? 520 AM (left), Calbryte? 590 AM (middle) or Calbryte? 630 AM (right) in HHBS with 2 mM probenecid were added into the wells, and the cells were incubated at 37 °C for one hour. The dye loading mediums were replaced with 200 μL HHBS, treated with 50 μL of 50 μM ATP, and imaged with a fluorescence microscope (Keyence) using FITC channel (Calbryte? 520), TRITC channel (Calbryte? 590) or Texas Red channel (Calbryte? 630).