End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I)-catalyzed azide–alkyne cycloaddition

• Ronald Okoth and
• Amit Basu

Beilstein J. Org. Chem. 2013, 9, 608–612, doi:10.3762/bjoc.9.66

• acid at the polymer terminus [6], a cis-alkene pentafluorophenol ester based terminating agent that introduces an amine-reactive capping agent [13], and cis-olefin terminating agents that directly introduce biotin and fluorescein at the polymer terminus [14]. A recent report describes the use of a cis

Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide

• Lena Möller,
• Christian Hess,
• Jiří Paleček,
• Yi Su,
• Axel Haverich,
• Andreas Kirschning and
• Gerald Dräger

Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33

• cycloadditions, the model compound fluoresceinyl azide 9[29][30] was first coupled to TPX derivatives 7a or 7b, under identical conditions as described for cRGD peptide 1b. The resulting polymers 8c and 8d were studied by determining the UV absorption peaks of fluorescein between 400 and 600 nm (Figure 4

• ). Absorption maxima of fluorescein were located at 457 nm and 481 nm, which can be ascribed to the presence of two isomeric forms (lacton versus carboxylate) of fluorescein [31]. These measurements clearly revealed the successful covalent functionalization of TPX with fluorescein by 1,3-dipolar cycloaddition

• . The copper-catalyzed method provided material 8c, which showed a small but significant absorption maximum for fluorescein at about 515 nm (dotted line versus dashed line) compared to starting TPX 7a. In contrast, the copper-free method led to intense fluorescein staining (polymer 8d, continuous line

A chemist and biologist talk to each other about caged neurotransmitters

• Graham C.R. Ellis-Davies

Beilstein J. Org. Chem. 2013, 9, 64–73, doi:10.3762/bjoc.9.8

• of uncaging involves two completely distinct properties [80]. First, we must consider how well a molecule absorbs light, through the molar extinction coefficient, ε. This property measures how effectively a chromophore absorbs photons. Thus, fluorescein (ε = 80,000/M/cm) absorbs light much better

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• variety of analytes, and specific markers of cellular organelles and other components. Although many structurally diverse fluorophores have been reported, many common fluorophores such as dianionic fluorescein (1, Figure 1) are defined by highly polar conjugated π systems. This high polarity confers

• substantial aqueous solubility, which is beneficial for some applications, such as protein labeling, but also results in low cellular permeability in assays involving living cells. Hydrophobic analogues of fluorescein such as Tokyo Green (2) [2], Pennsylvania Green (3) [3][4], and others [5] have been

• ) are renowned for their red-shifted fluorescence, photostability, and high quantum yields over a wide range of pH values (i.e., pH 4–10). These fluorophores penetrate cells more readily than analogous fluorescein derivatives, because the negative plasma membrane potential within the cytoplasm of cells

Bioorthogonal metabolic glycoengineering of human larynx carcinoma (HEp-2) cells targeting sialic acid

• Arne Homann,
• Riaz-ul Qamar,
• Sevnur Serim,
• Petra Dersch and
• Jürgen Seibel

Beilstein J. Org. Chem. 2010, 6, No. 24, doi:10.3762/bjoc.6.24

• ester, azido-fluorescein (14). For the metabolic labelling of eukaryotic cells, HEp-2 cells were incubated in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal calf serum (FCS). At 80% confluence they were split into 6-well plates with DMEM containing the functionalized carbohydrates (Ac4GlcNAz

• detectable. In order to analyze the natural background fluorescence of HEp-2, one sample was incubated without any additional carbohydrates. The cells were analyzed by fluorescence microscopy (580 nm for TAMRA staining and at 525 nm for fluorescein). At either wavelength, the negative control does not show

• [M-H]- calculated for C14H21NO9[H]- 360.13, found 360.2. Benzoic acid 2-[6-(3-azidopropanyloxy)-3-oxo-3H-xanthen-9-yl] 3-azidopropanyl ester, azido-fluorescein (14) Iodopropyl azide (210 mg, 26 mmol) was added to a solution of fluorescein (1g, 2.6mmol) in a mixture of distilled THF/MeOH (1:1, 25 mL