The complete mitochondrial genome of the green lizard Lacerta viridis viridis (Reptilia: Lacertidae) and its phylogenetic position within squamate reptiles.

For the first time the complete mitochondrial genome was sequenced for a member of Lacertidae. Lacerta viridis viridis was sequenced in order to compare the phylogenetic relationships of this family to other reptilian lineages. Using the long-polymerase chain reaction (long PCR) we characterized a mitochondrial genome, 17,156 bp long showing a typical vertebrate pattern with 13 protein coding genes, 22 transfer RNAs (tRNA), two ribosomal RNAs (rRNA) and one major noncoding region. The noncoding region of L. v. viridis was characterized by a conspicuous 35 bp tandem repeat at its 5' terminus. A phylogenetic study including all currently available squamate mitochondrial sequences demonstrates the position of Lacertidae within a monophyletic squamate group. We obtained a narrow relationship of Lacertidae to Scincidae, Iguanidae, Varanidae, Anguidae, and Cordylidae. Although, the internal relationships within this group yielded only a weak resolution and low bootstrap support, the revealed relationships were more congruent with morphological studies than with recent molecular analyses.

Physical principles of ultrasonic dissection and clinical application of BERCHTOLD SONO-CUT reusable ultrasonic scissors.

Technical principles and physical action mechanisms of ultrasonic dissection are introduced. We list various indications for using the BERCHTOLD SONO-CUT scissors and describe early clinical experiences, e.g. in pediatric laparoscopic surgery.

Isolation and crystallization of CP47, a Photosystem II chlorophyll binding protein. Degradation of CP47 upon dissociation from the core complex.

The CP47 protein was isolated from Photosystem II membranes by using a combination of the detergents n-dodecyl-beta-D-maltoside and octyl-beta-D-thioglucoside. The purified CP47 was used in a series of crystallization experiments, which yielded highly reproducible hexagonal crystals. Immunoblot analysis revealed that the isolated CP47 undergoes degradation even under dim light conditions. This degradation takes place after the protein has been dissociated from the core complex. Proteolysis experiments with trypsin demonstrated that the dissociation of the CP47 from the PS II core complex results in changes that render the protein sensitive to proteolysis.

Crystal structure of diisopropylfluorophosphatase from Loligo vulgaris.

BACKGROUND: Phosphotriesterases (PTE) are enzymes capable of detoxifying organophosphate-based chemical warfare agents by hydrolysis. One subclass of these enzymes comprises the family of diisopropylfluorophosphatases (DFPases). The DFPase reported here was originally isolated from squid head ganglion of Loligo vulgaris and can be characterized as squid-type DFPase. It is capable of hydrolyzing the organophosphates diisopropylfluorophosphate, soman, sarin, tabun, and cyclosarin. RESULTS: Crystals were grown of both the native and the selenomethionine-labeled enzyme. The X-ray crystal structure of the DFPase from Loligo vulgaris has been solved by MAD phasing and refined to a crystallographic R value of 17.6% at a final resolution of 1.8 A. Using site-directed mutagenesis, we have structurally and functionally characterized essential residues in the active site of the enzyme. CONCLUSIONS: The crystal structure of the DFPase from Loligo vulgaris is the first example of a structural characterization of a squid-type DFPase and the second crystal structure of a PTE determined to date. Therefore, it may serve as a structural model for squid-type DFPases in general. The overall structure of this protein represents a six-fold beta propeller with two calcium ions bound in a central water-filled tunnel. The consensus motif found in the blades of this beta propeller has not yet been observed in other beta propeller structures. Based on the results obtained from mutants of active-site residues, a mechanistic model for the DFP hydrolysis has been developed.

X-ray structure analyses of photosynthetic reaction center variants from Rhodobacter sphaeroides: structural changes induced by point mutations at position L209 modulate electron and proton transfer.

The structures of the reaction center variants Pro L209 --> Tyr, Pro L209 --> Phe, and Pro L209 --> Glu from the photosynthetic purple bacterium Rhodobacter sphaeroides have been determined by X-ray crystallography to 2.6-2.8 A resolution. These variants were constructed to interrupt a chain of tightly bound water molecules that was assumed to facilitate proton transfer from the cytoplasm to the secondary quinone Q(B) [Baciou, L., and Michel, H. (1995) Biochemistry 34, 7967-7972]. However, the amino acid exchanges Pro L209 --> Tyr and Pro L209 --> Phe do not interrupt the water chain. Both aromatic side chains are oriented away from this water chain and interact with three surrounding polar side chains (Asp L213, Thr L226, and Glu H173) which are displaced by up to 2.6 A. The conformational changes induced by the bulky aromatic rings of Tyr L209 and Phe L209 lead to unexpected displacements of Q(B) compared to the wild-type protein. In the structure of the Pro L209 --> Tyr variant, Q(B) is shifted by approximately 4 A and is now located at a position similar to that reported for the wild-type reaction center after illumination [Stowell, M. H. B., et al. (1997) Science 276, 812-816]. In the Pro L209 --> Phe variant, the electron density map reveals an intermediate Q(B) position between the binding sites of the wild-type protein in the dark and the Pro L209 --> Tyr protein. In the Pro L209 --> Glu reaction center, the carboxylic side chain of Glu L209 is located within the water chain, and the binding site of Q(B) remains unchanged compared to the wild-type structure.

Crystallization and preliminary X-ray crystallographic analysis of DFPase from Loligo vulgaris.

'Squid-type' diisopropylfluorophosphatases (DFPases), a subclass of the phosphotriesterases, are enzymes capable of hydrolysing organophosphorus nerve agents. To date, no three-dimensional structure of a 'squid-type' DFPase is known. Here, the crystallization of the DFPase originally isolated from head ganglion of the squid Loligo vulgaris is reported. The protein has been heterologously expressed in Escherichia coli, purified to homogeneity and subsequently crystallized. The protein crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 43.1, b = 82.1, c = 86.6 A and one monomer per asymmetric unit. Under cryoconditions (120 K) the crystals diffracted beyond 2.0 A using a Cu rotating-anode X-ray generator.

The natural product capsaicin inhibits photosynthetic electron transport at the reducing side of photosystem II and purple bacterial reaction center: structural details of capsaicin binding.

Capsaicin, a natural quinone analog, was found to block electron transport, in both plant photosystem II (PSII) and bacterial reaction center (RC) from Rhodobacter sphaeroides, at the QB site. The mode of action of capsaicin was investigated by O2 evolution measurements and fluoresence induction studies in the case of PSII, and flash-induced absorbance spectroscopy in the case of the bacterial RC. Structural details of capsaicin binding to the bacterial RC complex were determined by X-ray crystallographic analysis.

Structure of the photosynthetic reaction centre from Rhodobacter sphaeroides reconstituted with anthraquinone as primary quinone Q(A).

In the photosynthetic reaction centre (RC) from the purple bacterium Rhodobacter sphaeroides, the primary quinone, a ubiquinone-10 (Q(A)), has been substituted by anthraquinone. Three-dimensional crystals have been grown from the modified RC and its structure has been determined by X-ray crystallography to 2.4 A resolution. The bindings of the head-group from ubiquinone-10 and of the anthraquinone ring are very similar. In particular, both rings are parallel to each other and the hydrogen bonds connecting the native ubiquinone-10 molecule to AlaM260 and HisM219 are conserved in the anthraquinone containing RC. The space of the phytyl tail missing in the anthraquinone exchanged RC is occupied by the alkyl chain of a detergent molecule. Other structural changes of the Q(A)-binding site are within the limit of resolution. Our structural data bring strong credit to the very large amount of spectroscopic data previously achieved in anthraquinone-replaced RCs and which have participated in the determination of the energetics of the quinone system in bacterial RCs.

Identification of a hydrogen bond in the phe M197-->Tyr mutant reaction center of the photosynthetic purple bacterium Rhodobacter sphaeroides by X-ray crystallography and FTIR spectroscopy.

In bacterial reaction centers the charge separation process across the photosynthetic membrane is predominantly driven by the excited state of the bacteriochlorophyll dimer (D). An X-ray structure analysis of the Phe M197-->Tyr mutant reaction center from Rhodobacter sphaeroides at 2.7 A resolution suggests the formation of a hydrogen bond as postulated by Wachtveitl et al. [Biochemistry 32, 12875-12886, 1993] between the Tyr M197 hydroxy group and one of the 2a-acetyl carbonyls of D. In combination with electrochemically induced FTIR difference spectra showing a split band of the pi-conjugated 9-keto carbonyl of D, there is clear evidence for the existence of such a hydrogen bond.

Stereospecificity in contraluminal and luminal transporters of organic cations in the rat renal proximal tubule.

The effect of chirality on the interaction of substrates with the organic cation transporters in the proximal tubule of rat kidney was investigated. The apparent Ki values of the enantiomers/diastereomers of ephedrine and norephedrine and the stereoisomers of deprenyl, tranylcypromine, disopyramide, verapamil, pindolol and quinine/quinidine were determined against the contraluminal organic cation transporter, the luminal H+/organic cation exchanger and the luminal choline+ transporter, using the stop-flow luminal or contraluminal capillary microperfusion method. The ephedrine/norephedrine enantiomers/diastereomers had apparent Ki values against the contraluminal organic cation transporter in the range of 0.8 to 2.4 mM, and only norpseudoephedrine showed significant enantioselectivity. The same substrates had apparent Ki values against the luminal H+/organic cation exchanger between 3.0 and 15.0 mM, and ephedrine, norephedrine and norpseudoephedrine showed enantioselectivity. The Ki values against the luminal choline+ transporter were even higher (7.2-19.1 mM) and demonstrated no enantioselectivity. The verapamil and deprenyl enantiomers showed selectivity against the luminal choline+ transporter, as did quinine and quinidine against the contraluminal organic cation transporter. In all other instances enantioselectivity was not observed. In no case was the difference in the Ki values of the enantiomers/isomers greater than a factor of 3. The data confirm the high degree of nonspecificity of the renal organic cation transporters. Evaluation of three-dimensional molecular models of the ephedrine enantiomers/diastereomers suggests that the spatial orientations of the amino group and, to a lesser extent, the OH group and possibly the terminal CH3 group are of importance for different interactions with the transporters.

Shift of the special pair redox potential: electrostatic energy computations of mutants of the reaction center from Rhodobacter sphaeroides.

Shifts of the special pair redox potential of the photosynthetic reaction center of Rhodobacter sphaeroides are considered for several point mutations [Lin. X., Murchison, H. A., Nagarijan, V., Parson, W. W., Allen, J. P., & Williams, J. C. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 10265-10269] in the neighborhood of the special pair. The shifts are calculated from electrostatic energies by solving Poisson's equation for energy-minimized structures of the reaction center. Different conditions for the evaluation of the electrostatic energy are probed. To test the influence of the hydrogen bonding at the acetyl groups of the special pair, the orientation and torsion potential of the acetyl groups are varied. The calculated shifts of the midpoint potential of double and triple mutants can approximately be obtained from the corresponding shifts of the single point mutations. The calculated shifts agree with the measured values for all single and double mutants considered. However, a clear decision between different acetyl group conformations was only possible for the mutants HF(L168) and HF(L168) + LH(L131) where the calculated shifts of the redox potential agree with experiments only if the acetyl oxygen atom at DM points toward the Mg2+ ion of DL. This is corroborated by computations of the interaction energy of the acetyl group at DM, which adopts a lower value in the wild-type reaction center if its oxygen atom is bonded to the Mg2+ ion of DL.

Structure of the photosynthetic reaction centre from Rhodobacter sphaeroides at 2.65 A resolution: cofactors and protein-cofactor interactions.

BACKGROUND: Photosynthetic reaction centres (RCs) catalyze light-driven electron, transport across photosynthetic membranes. The photosynthetic bacterium Rhodobacter, sphaeroides is often used for studies of RCs, and three groups have determined the structure of its reaction centre. There are discrepancies between these structures, however, and to resolve these we have determined the structure to higher resolution than before, using a new crystal form. RESULTS: The new structure provides a more detailed description of the Rb. sphaeroides RC, and allows us to compare it with the structure of the RC from Rhodopseudomonas viridis. We find no evidence to support most of the published differences in cofactor binding between the RCs from Rps. viridis and Rb. sphaeroides. Generally, the mode of cofactor binding is conserved, particularly along the electron transfer pathway. Substantial differences are only found at ring V of one bacteriochlorophyll of the 'special pair' and for the secondary quinone, QB. A water chain with a length of about 23 A including 14 water molecules extends from the QB to the cytoplasmic side of the RC. CONCLUSIONS: The cofactor arrangement and the mode of binding to the protein seem to be very similar among the non-sulphur bacterial photosynthetic RCs. The functional role of the displaced QB molecule, which might be present as quinol, rather than quinone, is not yet clear. The newly discovered water chain to the QB binding site suggests a pathway for the protonation of the secondary quinone QB.

Medicotechnical basics of surgery using invasive ultrasonic energy.

Surgical techniques that use invasive ultrasonic energy for dissection and aspiration are a most advantageous extension of the methodological spectrum of conventional and endoscopic surgery. This article presents the technico-physical basics of the technology of ultrasonic surgery and the specific mechanisms underlying its effects on biologic tissue. A synopsis is given of the main fields of application of the ultrasonic aspirator in various surgical disciplines.

Polysubstrates: substances that interact with renal contraluminal PAH, sulfate, and NMeN transport: sulfamoyl-, sulfonylurea-, thiazide- and benzeneamino-carboxylate (nicotinate) compounds.

Some N-containing xenobiotics were recently shown to behave as bisubstrates; that is, they interact with and are transported by both the contraluminal transport system for organic anions (PAH) and the contraluminal transport system for organic cations (NMeN). Thus we determined whether other classes of N-containing substrates, such as sulfamoyl-, sulfonylurea-, thiazide- and benzeneamino-carboxylate (nicotinate) compounds, amongst them diuretics and other drugs, also interact with both transporters. To test this, we applied the stop-flow peritubular capillary perfusion method with initial flux measurements and determined app. Ki values for these substrates on PAH, sulfate and NMeN transport. We found that the following compounds interact with 1) the PAH transporter: benzene carboxylates, benzenesulfonylureas and benzenesulfonamides (as long as their acid pKa value is below 9.5). 2) the sulfate transporter: 2-anilinobenzoates, benzenesulfonylureas, polysubstituted sulfamoylbenzoates and some sulfamoylthiazides with electronegative charge accumulation around an anionic site. 3) the NMeN transporter: anilinobenzoates, sulfamoylbenzoates and benzenesulfonamides, if they bear an N-containing pyridine, pyrrolidine, furylmethylamino or thiazide group. There are, however, exceptions when H-bond formation might be responsible for interaction with that transporter. The data confirm the specificity rule for each transporter and the concept that one and the same substrate can match the requirements for several transporters. Thus the loop diuretics furosemide and piretanide, the thiazide diuretics hydrochlorothiazide, cyclopenthiazide and bendroflumethiazide and the sulfonylureas tolbutamide, chlorpropamide and torasemide interact with all three tested transport systems for PAH, sulfate and NMeN. Therefore, they are able to accomplish complex transport interactions with different transporters.

Cloning of a membrane-associated protein which modifies activity and properties of the Na(+)-D-glucose cotransporter.

An expression library from porcine kidney cortex was screened with a monoclonal antibody (R4A6) which stimulates high-affinity phlorizin binding in kidney and intestine but does not react with the membrane protein (SGLT1) which mediates Na(+)-coupled transport of D-glucose (Hediger, M.A., Coady, M.J., Ikeda, T.S., and Wright, E.M. (1987) Nature 330, 379-381). A cDNA (RS1) was obtained which codes for a hydrophilic M(r) 66,832 polypeptide and contains a predicted hydrophobic alpha-helix at the COOH terminus. After expression in Xenopus oocytes RS1 protein was found associated with the plasma membrane. RS1-homologous mRNAs were detected in renal outer cortex and outer medulla, small intestine, liver, and LLCPK1 cells, but not in skeletal muscle, heart muscle, Madin-Darby canine kidney (MDCK) cells, renal inner medulla, and Xenopus oocytes. After nondenaturing gel electrophoresis of renal brush-border membranes comigration of RS1- and SGLT1-homologous proteins as a high molecular weight complex was demonstrated. RS1 altered the expression of Na(+)-glucose cotransport by SGLT1 in Xenopus oocytes. There was no effect on the expression of the nonhomologous transporters for Na(+)-gamma-aminobutyric acid cotransport and for Na(+)-independent glucose transport. However, RS1 also changed the expression of the SGLT1-homologous Na(+)-myo-inositol cotransporter from MDCK cells. The Vmax of methyl-alpha-D-glucopyranoside (AMG) transport expressed after injection of a small amount of SGLT1-cRNA was increased 40-fold when a stoichiometric amount of RS1-cRNA was coinjected. In addition the voltage and glucose dependence of expressed AMG uptake and the concentration dependence of transport inhibition by phlorizin were changed when stoichiometric amounts of RS1-cRNA were coinjected with SGLT1-cRNA. Thus with SGLT1 one apparent transport site (K0.5 about 100 microM) and one apparent phlorizin inhibition site (Ki about 5 microM) was observed whereas with SGLT1 plus RS1 two apparent transport sites (K0.5(1) about 20 microM, K0.5(2) about 1 mM) and two apparent phlorizin inhibition sites (Ki(1) about 0.3 microM, Ki(2) about 30 microM) were found as has been described in brush-border membrane vesicles of kidney and intestine (see e.g. Koepsell, H., Fritzsch, G., Korn, K., and Madrala, A. (1990) J. Membr. Biol. 114, 113-132). The data suggest that the Na(+)-D-glucose cotransporter and possibly also other SGLT1-type Na(+)-cotransporters contain RS1-type regulatory subunits.

Bisubstrates: substances that interact with renal contraluminal organic anion and organic cation transport systems. I. Amines, piperidines, piperazines, azepines, pyridines, quinolines, imidazoles, thiazoles, guanidines and hydrazines.

In order to evaluate whether N-containing substrates interact with the organic "anion" (p-aminohippurate, PAH) or only with the organic "cation" (N1-methylnicotinamide, NMeN) transport system or with both, the stop-flow peritubular capillary microperfusion method was applied in the rat kidney in situ and the apparent Ki values of several classes or organic substrate against contraluminal NMeN and PAH transport were determined. Organic "anion" and organic "cation" transport are in inverted commas because neither transporter sees the degree of ionization in bulk solution, and they also accept nonionizable substrates [Ullrich KJ, Rumrich G (1992) Pflügers Arch 421:286-288]. Amines must be sufficiently hydrophobic (phenylethylamine, piperidine, piperazine) in order to interact with NMeN transport. Additional Cl, Br, NO2 or other electronegative groups render them inhibitory towards PAH transport also. Such bisubstrate amines were identified as follows: metoclopramide, bromopride, diphenhydramine, bromodiphenhydramine, verapamil, citalopram, ketamine, mefloquine, ipsapirone, buspirone, trazodone, H7 and trifluoperazine. Imidazole analogues interact with both transporters if they bear sufficiently hydrophobic alkyl or aryl groups or electronegative sidegroups. Bisubstrate imidazole analogues are tinidazole, pilocarpine, clonidine, azidoclonidine and cimetidine. Pyridines and thiazoles interact with the NMeN transporter if they have an additional ring-attached NH2 group. Again with an additional Cl, Br, or NO2 group the aminopyridines and aminothiazoles also become inhibitors for the PAH transporter. Amongst the guanidines only substances with several electronegative side-groups such as guanfacine, amiloride, benzylamiloride and ranitidine, interact with both transporters. Amongst the phenylhydrazines only 4-bromophenylhydrazine interacts with the NMeN transporter and 4-nitrophenylhydrazine with both transporters. Quinoline (isoquinoline) and its amino and hydroxy analogues interact with both transporters, their pKa values correlate directly with the affinity to the NMeN transporter and reciprocally with their affinity to the PAH transporter. In experiments with labelled substrates only the sufficiently hydrophilic cimetidine, amiloride and ranitidine show a saturable transport, which can be inhibited by probenecid (apalcillin) and tetraethylammonium in an additive manner. The highly hydrophobic substrates verapamil, citalopram, imipramine, diltiazem and clonidine enter the cell very fast in an unsaturable and uninhibitable manner, apparently in the undissociated form, since N-methyl-4-phenylpyridinium, which--disregarding its ionization--is similarly hydrophobic, shows a transport behaviour similar to that of tetraethylammonium [Ullrich et al. (1991) Pflügers Arch 419:84-92]. Ethidium bromide and dimidium bromide, which have a permanent cationic quaternary nitrogen and two sufficiently electronegative NH2 groups, also interact with both transporters.(ABSTRACT TRUNCATED AT 400 WORDS)

Bisubstrates: substances that interact with both, renal contraluminal organic anion and organic cation transport systems. II. Zwitterionic substrates: dipeptides, cephalosporins, quinolone-carboxylate gyrase inhibitors and phosphamide thiazine carboxylates; nonionizable substrates: steroid hormones and cyclophosphamides.

In order to test what chemical structure is required for a substrate to interact not only with the contraluminal organic anion (p-aminohippurate, PAH) transporter, but also with the organic cation (N1-methylnicotinamide, NMeN, or tetraethylammonium, TEA) transporter, the stop-flow peritubular capillary perfusion method was applied and app. Ki values were evaluated. Zwitterionic hydrophobic dipeptides not only interact with PAH but also with NMeN transport although with lower inhibitory potency (Ki,PAH = 0.2-1.4; Ki,NMeN 6-14 mmol/l). Amongst the zwitterionic cephalosporins, which all inhibit PAH transport, the amino cephalosporin analogue cefadroxil was identified to interact also with NMeN transport (Ki,PAH = 3.0, Ki,NMeN = 11.2 mmol/l). All zwitterionic naphthyridine and oxochinoline gyrase inhibitors tested inhibit NMeN transport with app. Ki,NMeN values between 1.2 mmol/l and 4.7 mmol/l; the naphthyridine analogues show a good inhibitory potency against PAH transport (Ki,PAH approximately 0.4 mmol/l), the piperazine-containing quinolone analogues have a moderate inhibitory potency (Ki,PAH = 1.1-2.5 mmol/l) and the piperazine-containing pipemidic acid did not inhibit PAH transport at all. Zwitterionic thiazolidine carboxylate phosphamides also interact with both transporters (app. Ki,PAH approximately 3.0; app. Ki,NMeN approximately 18.0 mmol/l). The nonionizable oxo- and hydroxy-group-containing corticosteroid hormones also interact with the two transporters. (a) An OH group in position 21 is necessary for interaction with the PAH transporter, but not for interaction with the TEA transporter. (b) Introduction of an OH group in position 17 alpha abolishes interaction with the TEA transporter, but has different effects with the PAH transporter. (c) Introduction of an OH group in position 6 abolishes interaction with both, the PAH and the TEA transporter. (d) A change of the side-group in position 11 of corticosterone from -OH to -H to = O enhances interaction with the PAH transporter but has no effect on the interaction with the TEA transporter. Nonionizable 4- or 5-androstene analogues inhibit both transporters with app. Ki between 0.16 mmol/l and 0.64 mmol/l, if the steroids are soluble in a concentration greater than 1 mmol/l. Nonionizable oxazaphosphorins with more than one chloroethyl group interact with the PAH transporter with app. Ki between 0.84 mmol/l and 4.9 mmol/l and with the NMeN transporter with app. Ki between 3.2 mmol/l and 18.7 mmol/l. Thus a substrate interacts with both transporters if it is sufficiently hydrophobic, possesses acidic and/or electron-attracting plus basic and/or electron-donating groups, or possesses several electron-attracting nonionizable groups (O, OH, Cl). A certain spatial arrangement of the interacting groups seems to be necessary.

New crystal form of the photosynthetic reaction centre from Rhodobacter sphaeroides of improved diffraction quality.

Trigonal crystals of photosynthetic reaction centres from the wild-type purple bacterium, Rhodobacter sphaeroides (ATCC 17023), have been grown from potassium phosphate solutions at 18 degrees C. They belong to the space group P3(1/2)21 and have unit cell dimensions of a = b = 141.4 A and c = 187.2 A. The crystals diffract to at least 2.65 A resolution and are suitable for detailed structural studies.

Characterization of a Photosystem II core and its three-dimensional crystals.

A photosystem II core from spinach containing the chlorophyll-binding proteins 47 kDa, 43 kDa, the reaction center proteins D1, D2 and cytochromeb 559 and three low molecular weight polypeptides (MW < 10 kDa) was isolated, its three-dimensional crystals were prepared, and both core and crystals were studied by spectroscopic techniques and electron microscopy. The absorption spectra of the crystallized form of the core indicate a specific orientation of the various pigments within the crystal.

Inhibition of anion transport in the human red blood cell membrane with para- and meta-methoxyphenylglyoxal.

The positional isomers para-methoxyphenylglyoxal and meta-methoxyphenylglyoxal were newly synthesized and found to be potent inhibitors of sulfate exchange in the red blood cell membrane. The rate of inactivation of the transport system with both reagents obeys pseudo-first-order kinetics and increases with increasing pH and reagent concentration. The degree of inhibition of the transport system with the meta-isomer exceeds the inhibition caused by the para-isomer. At 2 mM 3-methoxyphenylglyoxal (3-MOPG) and 37 degrees C the half-lifetime of the anion transporter is 5.4 min at pH 8.0. Under the same experimental conditions the half-lifetime of the transporter at 2 mM 4-methoxyphenylglyoxal (4-MOPG) is found to be 24.7 min. The binding site of these reagents is found to be the same as binding site of the reversibly acting phenylglyoxal derivative 4-hydroxy-3-nitrophenylglyoxal (HNPG). Chloride ions are able to protect the transporter against inhibition with both reagents. Anion transport inhibitors like 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS) and flufenemate, which are known to act on band 3 protein, are able to interact with the binding of the newly synthesised reagents. Phloretin and phloridzin show no interaction.