Intensity Probes

		Excitation Light Sources												Characteristics						Characteristics
Product Number (Specs Sheet)	Product Name (Product Info)	380	405	436	488	532	594	635	650	680	700	750	780	Medium	λ abs [nm]	ε [M –1 cm–1]	λ em [nm]	QY [%]	FLT [ns]	Medium	λ abs [nm]	ε [M–1 cm–1]	λ em [nm]	QY [%]	FLT [ns]	Buy
K35 K35	K35 K35	•	•	•										Toluene	410	10,000	495	60		EtOH	430	13,200	552	0.01
K6-207 K6-207	3-DAB 3-DAB		•	•	•									Toluene	445	9,700	582	43		EtOH	460	8,600	665	22	4.0
K6-208 K6-208	2-DAB 2-DAB		•	•	•									Toluene	464	3,600	551	31		EtOH	480	2,900	670	1.1
K8-1350 K8-1350	Square-670-Carboxy Square-670-Carboxy	•	•					•	•					PB 7.4	656		676	1.7	0.29	6g/L BSA	673		693	29
K8-1351 K8-1351	Square-660-Carboxy Square-660-Carboxy	•	•					•	•					PB 7.4	657	182,000	676	3	0.27	2g/L BSA	679	182,000	696	45	3.56
K8-1355 K8-1355	Square-680-Carboxy Square-680-Carboxy	•	•					•	•	•				PB 7.4	654	138,000	670	1		1g/L BSA	688	168,000	708	62
K8-1440 K8-1440	Square-670 Square-670	•	•	•				•	•	•				pH 7.4	659		677	0.09		1 g/L BSA	683		702	50
K8-1443 K8-1443	Square-730 Square-730	•	•	•	•					•	•			CHCl3	728	166,000	757	46		1g/L BSA	722		745
K8-1500 K8-1500	Square-655 Square-655	•	•					•	•					PB 7.4	622	177,000	644	0.09		1 g/L BSA	652	188	672	80
K9-4145 K9-4145	SeTau-633-Ethyl-Ester SeTau-633-Ethyl-Ester							•	•					CHCl3	634	105,000	683	68
K9-4150 K9-4150	SeTau-647 SeTau-647							•	•					PB 7.4	647	211,000	693	59	3.1	PB 7.4	647	211,000	693	59	3.1
K8-3010 K8-3010	Square-460 Square-460	•	•	•	•									PB 7.4	467	50,000	515	0.9		6g/L BSA	469		512	8.6
K8-1405 K8-1405	Square-650-pH-Carboxy Square-650-pH-Carboxy						•	•	•					PB 5.6	653	135,000	671	16	1.17	pH 9.0	535	48,000	663	9	0.53
K8-1610 K8-1610	Square-635-Carboxy Square-635-Carboxy						•	•						pH 7.4	634	180,000	646	9		pH 12.0	520		-	-	-
K8-1665 K8-1665	Seta-635-pH-di-Carboxy Seta-635-pH-di-Carboxy							•						PB 7.4	640	188,000	656	33	1.8	pH 12.0	519		-	-	-
K8-1365 K8-1365	Seta-670-pH-di-Carboxy Seta-670-pH-di-Carboxy	•	•					•	•	•				PB 6.0	672	93,000	694	19		pH 11.5	535		-	-	-
K6-1037 K6-1037	K37 K37		•	•										Toluene	434	29,500	540	49		Cholesterol in water			540
K8-2100 K8-2100	YOSeta-1 (1mM solution in DMSO) YOSeta-1 (1mM solution in DMSO)				•									dsDNA	492	98,800	509	52

^new Staining of double-stranded DNA: YOSeta-1 is a cell-impermeant fluorescent dye used for staining of double-stranded DNA (same dye as YOYO® 1). The free YOSeta-1 dye has a very low fluorescence quantum yield but the QY increases several thousand times upon binding to double-stranded DNA (see specs sheet). The probe is available as a 1 mM solution in DMSO.

Absorption and emission spectrum of YOSeta-1 in presence of dsDNA

Measurement of changes in lipid bilayer hydration in cells: Square-670 is as an effective red emitting fluorescent probe for examining membrane-related processes, e.g. drug-influenced changes in bilayer hydration [18​].

Protein analysis: Dyes such as Square-655 and Square-680 exhibit a substantial fluorescence intensity increase (up to 190 times) in the presence of BSA. Fluorescence enhancement of the dyes in the presence of other albumins (HSA and ovalbumin) is lower (40 times). The large fluorescence enhancement in presence of proteins makes them valuable dyes for the visualization and quantification of proteins in gel-electrophoresis applications.

Square dyes are the most sensitive dyes on the market for the detection of proteins. The protein-bound forms of Square dyes exhibit absorption and emission maxima between 640 and 750 nm, very high extinction coefficients between 104,000–208,000 M^–1cm^–1 and quantum yields as high as 80%.

Squaraine-Rotaxane imaging probes for live and fixed cells: Our fluorescent rotaxane probes exhibit extremely high chemical and photochemical stability and are therefore well suited for imaging applications. They also exhibit very high 2-photon action cross sections in the order of several thousand GM.

SeTau-633 is a carboxylic acid ethyl ester derivative that passively penetrates cell membranes. Once inside these residue are hydrolyzed by esterases thereby forming carboxyl groups that are cell-impermeable.

SeTau-647 is a highly water-soluble fluorescent probe with several negative charges and therefore will not passively penetrate the cell-menbrane. This probe is very photostable and has a quantum yield of 60% in water.

Reactive versions (NHS-esters and maleimides) for covalent attachment to different biomolecules to target specific cellular locations for in vitro and in vivo optical imaging are also available. Images stained with these probes are stable for hundreds of hours:

[B.D. Smith et al. Squaraine Rotaxanes: Superior Substitutes for Cy-5 in Molecular Probes for Near-Infrared Fluorescence Cell Imaging. Angew. Chem. 2007, 119, 5624 –5627].

pH-measurement in cells: Probes such as Square-650-pH-Carboxy exhibit pKa’s in the physiologically relevant pH range and are therefore useful to measure the intercellular pH changes in cells. For more information about this dye we refer you to the specs sheet of Square-650-pH-Carboxy  and the published literature.

Titration curves for Square-635, Seta-635-pH and Seta-670-pH in presence of dsDNA

Additional pH-probes with pKa's in the alkaline pH-range are listed under pH-sensing applications.

Albumin Determination: K35 and Square-655 are a fluorescent probes for determination of albumin binding sites in plasma and serum [19, 20]. The fluorescence intensity of these probes significantly increases in presence of albumin.

Probes for the evaluation of cryoprotection:

Cryoprotectors (CPs) are important reagents that help to prevent biological matter such as blood, tissues and cells from degradation during low-temperature storage. Fluorescent dyes are useful tools to investigate the interaction of CPs with biological species. Long-term and low temperature storage of cells is an important process for biomedical research and transplantation medicine. Biomembranes are cellular structures that are strongly affected by the freeze-thawing process.

The freeze-thawing experiments with yeast cells using cryoprotectors have demonstrated that 2-DAB and 3-DAB are fluorescent probes that enable not only to distinguish damaged from undamaged cells, but also allow quantitative estimation of the extent of damage by the cryogenic treatment. These fluorescent probes are therefore very useful to quickly assess the effects of cryopreservation on cells using fluorescence imaging.

See also Fluorescence Imaging, NIR Fluorescence Imaging and Fluorescence Lifetime Imaging.