SGFP2荧光蛋白是一种绿色荧光蛋白变体，发表于2007年，来源于维多利亚水母。SGFP2绿色荧光蛋白激发光波长495nm，发射光波长512nm，可以用蓝光激发。SGFP2绿色荧光蛋白具有中度酸敏感性，大小为26.9kDa。

SGFP2绿色荧光蛋白的研究与发现

荧光蛋白已成为细胞生物学中非常宝贵的工具。绿色荧光蛋白变体EGFP的应用尤其广泛。然而，包括EGFP在内的荧光蛋白的使用可能会受到蛋白质折叠效率低下的阻碍，导致蛋白质聚集和荧光减少。这在原核细胞中尤其明显。此外，增强型绿色荧光蛋白EGFP的蓝色荧光蛋白变体EBFP因其微弱的荧光和快速的光漂白而很少使用。因此，努力提高蛋白质折叠、荧光亮度和光稳定性等性能非常重要。

2007年，阿姆斯特丹大学和荷兰乌特勒支大学的科研人员发表文献，关于改进绿色荧光蛋白和蓝色荧光蛋白在细菌和哺乳动物细胞中的表达。科研人员分别基于EGFP和EBFP创建了强增强绿色荧光蛋白（SGFP2）和强增强蓝色荧光蛋白（SBFP2）。科研人员使用定点突变引入了几种突变，这些突变被证明可以改善荧光蛋白EYFP和ECFP。

荧光蛋白SGFP2和SBFP2在体外表现出更快、更有效的蛋白质折叠和加速的发色团氧化。对于这两种强烈增强的荧光蛋白，其光稳定性提高了2倍，SBFP2的量子产率提高了3倍。提高的折叠效率降低了大肠杆菌中蛋白质聚集的程度，从而使表达SGFP2的细菌的亮度比表达EGFP的细菌的透明度提高了7倍。表达SBFP2的细菌比表达EBFP的细菌荧光强度高16倍。在哺乳动物细胞中，这种改善不太明显。表达SGFP2的细胞比表达EGFP的细胞亮1.7倍，这显然是由于更有效的蛋白质表达和/或发色团成熟。表达SBFP2的哺乳动物细胞比表达EBFP的细胞亮3.7倍。这种亮度的增加与纯化重组蛋白观察到的固有亮度的增加非常相似。荧光蛋白SGFP2和SBFP2的成熟效率和光稳定性的提高有助于检测并延长荧光成像的更大持续时间。

SGFP2绿色荧光蛋白的激发光和发射光

SGFP2绿色荧光蛋白激发光波长495nm，发射光波长512nm，可以用荧光手电筒GFPfinder-2101RB激发。

荧光手电筒GFPfinder-2101RB提供高强度蓝色激发光，可穿透培养皿，激发愈伤组织、菌落、细胞、植物、动物中表达的绿色荧光蛋白。GFP绿色荧光蛋白和EGFP增强型绿色荧光蛋白，都可以使用荧光手电筒进行快速检测。通过特制滤光片，可用肉眼观察绿色荧光，并拍摄清晰的荧光照片。

荧光手电筒GFPfinder-2101RB检测效率高、使用方便，价格仅为荧光显微镜的十分之一，是检测绿色荧光蛋白的理想设备，得到众多高校和科研机构的好评和认可！

下图：荧光手电筒GFPfinder-2101RB

SGFP2 Green Fluorescent Protein

Fluorescent proteins have become an invaluable tool in cell biology. The green fluorescent protein variant EGFP is especially widely applied. Use of fluorescent proteins, including EGFP, however can be hindered by inefficient protein folding, resulting in protein aggregation and reduced fluorescence. This is especially profound in prokaryotic cells. Furthermore, EBFP, a blue fluorescent protein variant of EGFP, is rarely used because of its dim fluorescence and fast photobleaching. Thus, efforts to improve properties such as protein folding, fluorescence brightness, and photostability are important. Strongly enhanced green fluorescent proteins (SGFP2) and strongly enhanced blue fluorescent proteins (SBFP2) were created, based on EGFP and EBFP, respectively. We used site-directed mutagenesis to introduce several mutations, which were recently shown to improve the fluorescent proteins EYFP and ECFP. Fluorescent proteins SGFP2 and SBFP2 exhibit faster and more efficient protein folding and accelerated chromophore oxidation in vitro. For both strongly enhanced fluorescent proteins, the photostability was improved 2-fold and the quantum yield of SBFP2 was increased 3-fold. The improved folding efficiency reduced the extent of protein aggregation in Escherichia coli, thereby increasing the brightness of bacteria expressing SGFP2 7-fold compared to the brightness of those expressing EGFP. Bacteria expressing SBFP2 were 16-fold more fluorescent than those expressing EBFP. In mammalian cells, the improvements were less pronounced. Cells expressing SGFP2 were 1.7-fold brighter than those expressing EGFP, which was apparently due to more efficient protein expression and/or chromophore maturation. Mammalian cells expressing SBFP2 were 3.7-fold brighter than cells expressing EBFP. This increase in brightness closely resembled the increase in intrinsic brightness observed for the purified recombinant protein. The increased maturation efficiency and photostability of SGFP2 and SBFP2 fluorescent proteins facilitate detection and extend the maximum duration of fluorescence imaging.

Reference:

Improved Green and Blue Fluorescent Proteins for Expression in Bacteria and Mammalian Cells

Kremers G-J, Goedhart J, Van Den Heuvel Dj, Gerritsen Hc, Gadella Twj (2007). Biochemistry, 46(12) , 3775-3783. doi: 10.1021/bi0622874.