COMMUNICATIONS
[3H]galactose from the donor UDP-Gal (50 mm) to the acceptor molecule
LacNAc(CH2)8CO2CH3 (0.36 mm) by the pa(1-3)GalT (10 mm) in an assay
buffer system consisting of sodium cacodylate (100 mm; pH 6.5), 15 mm
MnCl2, and BSA (bovine serum albumin; 50 mgmL 1) at 378C for 30 min.
The radiolabeled product, [3H]Gala(1-3)LacNAc(CH2)8CO2CH3, was
separated from unincorporated label by adsorption onto a SepPac C18
column[20]. The ratio of incorporated to total radioactivity is proportional
to the activity of pa(1-3)GalT. We took precautions to ensure that the
enzyme was the limiting reagent and that all other cofactors were close to
the saturation point. Strictly speaking, the reported inhibition is an IC50
value because we have not carried out the assays with different concen-
trations of cofactors.
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Received: April 9, 2001 [Z16925]
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Polyphenylene Dendrimers as Sensitive and
Selective Sensor Layers**
Martin Schlupp,* Tanja Weil, Alexander J. Berresheim,
Uwe M. Wiesler, Joachim Bargon,* and Klaus Müllen*
Polyphenylene dendrimers (PDs) are monodisperse macro-
molecules, whichÐbecause of their rigid frameworkÐcontain
internal voids. This property differentiates them from other
dendrimers, which consist of flexible, aliphatic groups, and
makes them attractive as selective layers for gravimetric
sensors. Such sensors based upon the quartz microbalance
(QMB)[1] are widely used to monitor the concentration of
various volatile organic compounds (VOCs) in different
environments. These types of sensors are of increasing
significance in many aspects of daily life, be it monitoring
the manufacture or storage of foodstuff,[2] controlling chem-
[5] a) L. M. Sinnott in Enzyme Mechanisms (Eds.: M. I. Page, A.
Williams), The Royal Society of Chemistry, London, 1987, pp. 259 ±
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Chem. 1989, 264, 17174 ± 17181; b) O. Hindsgaul, K. J. Kaur, G.
Srivastava, M. Blaszczyk-Thurin, S. C. Crawley, L. D. Heerze, M. M.
Palcic, J. Biol. Chem. 1991, 266, 17858 ± 17862.
[7] A socalled bisubstrate analogue of a(1-2)-fucosyltransferase that
lacked the fucose moiety was synthesized (ref. [6]) and exhibited low
inhibitory activity.
[*] Dr. M. Schlupp, Prof. Dr. J. Bargon
Institut für Physikalische und Theoretische Chemie, Universität Bonn
Wegelerstrasse 12, 53115 Bonn (Germany)
Fax : (49)228-73-9424
E-mail: schlupp@thch.uni-bonn.de, bargon@uni-bonn.de
[8] Closely related to the disubstrate analogue 1b for glycosyltransferase
inhibition are the recently published ketoside-based a(1-3)-fucosyl-
transferase inhibitors, which were termed trisubstrate analogues, even
though glycosyltransferases employ only two substrates and catalyze
irreversible reactions: B. M. Heskamp, G. H. Veeneman, G. A.
van der Marel, C. A. A. van Boeckel, J. H. van Boom, Tetrahedron
1995, 51, 8397 ± 8406; B. M. Heskamp, G. A. van der Marel, J. H.
van Boom, J. Carbohydr. Chem. 1995, 14, 1265 ± 1277; a b(1-4)gal-
actosyltransferase inhibitor was reported which follows an entirely
different design: H. Hashimoto, T. Endo, Y. Kajihara, J. Org. Chem.
1997, 62, 1914 ± 1922.
Prof. Dr. K. Müllen, T. Weil, Dr. A. J. Berresheim, Dr. U. M. Wiesler
Max-Planck-Institut für Polymerforschung
Ackermannweg 10, 55129 Mainz (Germany)
Fax : (49)6131-379-350
[**] This work has been supported by the TMR European Research
Program, through the SISITOMAS Project, by the Volkswagen
Foundation, the German Science Foundation (DFG), the German
Federal Ministry for Science and Technology (BMBF), and the Fonds
of the German Chemical Industry, Frankfurt (Main); U.M.W. thanks
the latter for a graduate fellowship, we all thank C. Beer and S. Spang
for valuable support during the syntheses.
[9] The first crystal structure of a retaining galactosyltransferase was
recently reported: K. Persson, H. D. Ly, M. Dieckelmann, W. W.
Angew. Chem. Int. Ed. 2001, 40, No. 21
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