Routine botulinum toxin injection one month after a Swenson pull-through does not change the incidence of Hirschsprung associated enterocolitis.

PURPOSE: Patients with Hirschsprung disease (HD) are at risk of Hirschsprung associated enterocolitis (HAEC) following pull-through. The purpose of this study was to determine if routine Botulinum toxin (BT) injected one-month post pull-through decreases the incidence of HAEC. METHODS: We reviewed patients who underwent a primary (not redo) pull-through operation for HD between April 2014 to December 2019. Over the most recent 18 months, BT was administered routinely one-month post-pull-through procedure; these patients were compared to the prior group that did not receive routine BT. A HAEC episode was defined as one that required initiation of treatment for obstructive symptoms in the inpatient or outpatient setting with antibiotics and irrigations. Categorical variables were compared using the nonparametric chi-square test or Fisher's exact test. Continuous variables were compared using the two-tailed Student's t-test. P-value <0.05 was determined to be statistically significant. RESULTS: A total of 70 patients underwent Swenson pull-through during the study period (52% male). There were no statistically significant differences in demographics in the BT vs. non-BT group. Routine post-pull-through BT was given in 28 patients and did not significantly change HAEC incidence compared to the non-BT group (12/28, 43% vs. 16/42, 38%. P = 0.691). Of note, the BT group patients developed HAEC significantly sooner than the patients in the non-BT group (37.5 days vs. 253 days, p = 0.029). More patients in the BT group (n = 18, 64%) required at least one subsequent BT injection compared to the patients in the non-BT group (n = 11, 26%. P = 0.001). CONCLUSIONS: We conclude that routine postoperative botulinum toxin injection given one month postoperatively from Swenson pull-through did not change the incidence of HAEC. A prospective controlled study is necessary to confirm these findings.

The Association of Enhanced Recovery Pathway and Acute Kidney Injury in Patients Undergoing Colorectal Surgery.

BACKGROUND: Acute kidney injury is associated with increased postoperative length of hospital stay and increases the risk of postoperative mortality. The association between the development of postoperative acute kidney injury and the implementation of an enhanced recovery after surgery protocol remains unclear. OBJECTIVE: This study aimed to examine the relationship between the implementation of an enhanced recovery pathway and the development of postoperative acute kidney injury. DESIGN: In this retrospective cohort study, a prospectively maintained database of patients who underwent elective colorectal surgery in an enhanced recovery pathway were compared to a hospital historical National Surgical Quality Improvement Program colorectal registry of patients. SETTINGS: This study was conducted at the University of Alabama at Birmingham, a tertiary referral center. PATIENTS: A total of 1052 patients undergoing elective colorectal surgery from 2012 through 2016 were included. MAIN OUTCOME MEASURES: The development of postoperative acute kidney injury was the primary outcome measured. RESULTS: Patients undergoing an enhanced recovery pathway had significantly greater rates of postoperative acute kidney injury than patients not undergoing an enhanced recovery pathway (13.64% vs 7.08%; p < 0.01). Our adjusted model indicated that patients who underwent an enhanced recovery pathway (OR, 2.31; 95% CI, 1.48-3.59; p < 0.01) had an increased risk of acute kidney injury. Patients who developed acute kidney injury in the enhanced recovery cohort had a significantly longer median length of stay than those who did not (median 4 (interquartile range, 4-9) vs 3 (interquartile range, 2-5) days; p=0.04). LIMITATIONS: This study did not utilize urine output as a modality for detecting acute kidney injury. Data are limited to a sample of patients from a large academic medical center participating in the National Surgical Quality Improvement Program. Interventions or programs in place at our institution that aimed at infection reduction or other initiatives with the goal of improving quality were not accounted for in this study. CONCLUSION: The implementation of an enhanced recovery after surgery protocol is independently associated with the development of postoperative acute kidney injury.See Video Abstract at http://links.lww.com/DCR/B69. LA ASOCIACIÓN DE VÍA DE RECUPERACIÓN MEJORADA Y LESIÓN RENAL AGUDA EN PACIENTES DE CIRUGÍA COLORRECTAL: La lesión renal aguda se asocia con una mayor duración en la estancia hospitalaria y aumenta el riesgo de la mortalidad postoperatoria. La asociación entre el desarrollo de la lesión renal aguda postoperatoria y la implementación de un protocolo de Recuperación Mejorada después de la cirugía, sigue sin ser clara.Examinar la relación entre la implementación de una vía de Recuperación Mejorada y el desarrollo de lesión renal aguda postoperatoria.Estudio de cohorte retrospectivo, de una base de datos mantenida prospectivamente, de pacientes que se sometieron a cirugía colorrectal electiva, en una vía de Recuperación Mejorada, se comparó con el registro histórico de los pacientes colorrectales del Programa Nacional de Mejora de la Calidad Quirúrgica.Universidad de Alabama en Birmingham, un centro de referencia terciario.Un total de 1052 pacientes sometidos a cirugía colorrectal electiva desde 2012 hasta 2016.Desarrollo de lesión renal aguda postoperatoria.Los pacientes sometidos a una vía de Recuperación Mejorada, tuvieron tasas significativamente mayores de lesiones renales agudas postoperatorias, en comparación con los pacientes de Recuperación no Mejorada (13.64% vs 7.08%; p < 0.01). Nuestro modelo ajustado indicó que los pacientes que se sometieron a una vía de Recuperación Mejorada (OR, 2.31; IC, 1.48-3.59; p < 0.01) tuvieron un mayor riesgo de lesión renal aguda. Los pacientes que desarrollaron daño renal agudo en la cohorte de Recuperación Mejorada, tuvieron una estadía mediana significativamente más larga en comparación con aquellos que no [mediana 4 (rango intercuartil (RIC) 4-9) versus 3 (RIC 2-5) días; p = 0.04].Este estudio no utilizó la producción de orina como una modalidad para detectar daño renal agudo. Los datos se limitan a una muestra de pacientes de un gran centro médico académico, que participa en el Programa Nacional de Mejora de la Calidad Quirúrgica. Las intervenciones o programas implementados en nuestra institución, destinados a la reducción de infecciones u otras iniciativas, con el objetivo de mejorar la calidad, no se tomaron en cuenta para este estudio.La implementación de una Recuperación Mejorada después del protocolo de cirugía, se asocia independientemente con el desarrollo de lesión renal aguda postoperatoria.Consulte Video Resumen en http://links.lww.com/DCR/B69. (Traducción-Dr. Fidel Ruiz-Healy).

An iron-oxygen intermediate formed during the catalytic cycle of cysteine dioxygenase.

Cysteine dioxygenase is a key enzyme in the breakdown of cysteine, but its mechanism remains controversial. A combination of spectroscopic and computational studies provides the first evidence of a short-lived intermediate in the catalytic cycle. The intermediate decays within 20 ms and has absorption maxima at 500 and 640 nm.

An investigation of bubble coalescence and post-rupture oscillation in non-ionic surfactant solutions using high-speed cinematography.

Most processes involving bubbling in a liquid require small bubbles to maximise mass/energy transfer. A common method to prevent bubbles from coalescing is by the addition of surfactants. In order to get an insight into the coalescence process, capillary bubbles were observed using a high speed cinematography. Experiments were performed in solutions of 1-pentanol, 4-methyl-2-pentanol, tri(propylene glycol) methyl ether, and poly(propylene glycol) for which information such as the coalescence time and the deformation of the resultant bubble upon coalescence was extracted. It is shown in this study that the coalescence time increases with surfactant concentration until the appearance of a plateau. The increase in coalescence time with surfactant concentration could not be attributed only to surface elasticity. The oscillation of the resultant bubble was characterised by the damping of the oscillation. The results suggested that a minimum elasticity is required to achieve an increased damping and considerable diffusion has a detrimental effect on the dynamic response of the bubble, thereby reducing the damping.

Chlorine dioxide oxidation of dihydronicotinamide adenine dinucleotide (NADH).

The oxidation of dihydronicotinamide adenine dinucleotide (NADH) by chlorine dioxide in phosphate buffered solutions (pH 6-8) is very rapid with a second-order rate constant of 3.9 x 10(6) M(-1) s(-1) at 24.6 degrees C. The overall reaction stoichiometry is 2ClO2(*) per NADH. In contrast to many oxidants where NADH reacts by hydride transfer, the proposed mechanism is a rate-limiting transfer of an electron from NADH to ClO2(*). Subsequent sequential fast reactions with H(+) transfer to H2O and transfer of an electron to a second ClO2(*) give 2ClO2(-), H3O(+), and NAD(+) as products. The electrode potential of 0.936 V for the ClO2(*)/ClO2(-) couple is so large that even 0.1 M of added ClO2(-) (a 10(3) excess over the initial ClO2(*) concentration) fails to suppress the reaction rate.

Molecular analysis of two cytochrome P450 monooxygenase genes required for paxilline biosynthesis in Penicillium paxilli, and effects of paxilline intermediates on mammalian maxi-K ion channels.

The gene cluster required for paxilline biosynthesis in Penicillium paxilli contains two cytochrome P450 monooxygenase genes, paxP and paxQ. The primary sequences of both proteins are very similar to those of proposed cytochrome P450 monooxygenases from other filamentous fungi, and contain several conserved motifs, including that for a haem-binding site. Alignment of these sequences with mammalian and bacterial P450 enzymes of known 3-D structure predicts that there is also considerable conservation at the level of secondary structure. Deletion of paxP and paxQ results in mutant strains that accumulate paspaline and 13-desoxypaxilline, respectively. These results confirm that paxP and paxQ are essential for paxilline biosynthesis and that paspaline and 13-desoxypaxilline are the most likely substrates for the corresponding enzymes. Chemical complementation of paxilline biosynthesis in paxG (geranygeranyl diphosphate synthase) and paxP, but not paxQ, mutants by the external addition of 13-desoxypaxilline confirms that PaxG and PaxP precede PaxQ, and are functionally part of the same biosynthetic pathway. A pathway for the biosynthesis of paxilline is proposed on the basis of these and earlier results. Electrophysiological experiments demonstrated that 13-desoxypaxilline is a weak inhibitor of mammalian maxi-K channels (Ki=730 nM) compared to paxilline (Ki=30 nM), indicating that the C-13 OH group of paxilline is crucial for the biological activity of this tremorgenic mycotoxin. Paspaline is essentially inactive as a channel blocker, causing only slight inhibition at concentrations up to 1 microM.

Viscosity effect on the structural compactness of latex flocs formed under weak depletion attractions.

Dilute aqueous dispersions of colloidal polystyrene latex spheres were flocculated by adding a nonadsorbing polymer sample, poly(acrylic acid). The structural compactness of the flocs thus formed was characterized in terms of their mass fractal dimension using the small-angle static light scattering technique. It was found that with low poly(acrylic acid) concentrations and thus weak depletion attraction forces, the dispersion medium viscosity had a marked effect on the floc structure. An increase in the viscosity led to formation of denser flocs. This was revealed in three sets of depletion flocculation experiments: (a) adjusting the background electrolyte concentration at a fixed level of poly(acrylic acid), (b) using water and 30% (w/w) glycerol as the respective solvents, and (c) inducing latex flocculation with two poly(acrylic acids) of different molecular weights at the respective critical polyacid concentrations. Direct force measurements were made with atomic force microscopy to isolate the influence of viscosity on floc structure from that of interparticle interaction energies. We conclude that the formation of denser flocs with increasing medium viscosity can be attributed to the reduced diffusivity of particles in the solution. The latter resulted in an enhanced rate of floc restructuring (through relaxation of attached particles) relative to floc growth.

Substrate deactivation of phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase by erythrose 4-phosphate.

3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS, EC 4.1.2.15) catalyzes the condensation of phosphoenolpyruvate (PEP) with erythrose 4-phosphate (E4P) to give DAH7P via an ordered sequential mechanism. In the absence of PEP (the first substrate to bind), E4P binds covalently to the phenylalanine-sensitive DAH7PS of Escherichia coli, DAH7PS(Phe), deactivating the enzyme. Activity is restored on addition of excess PEP but not if deactivation was carried out in the presence of sodium cyanoborohydride. Electrospray mass spectrometry indicates that a single E4P is bound to the protein. These data are consistent with a slow, reversible Schiff base reaction of the aldehydic functionality of E4P with a buried lysine. Molecular modeling indicates that Lys186, a residue at the base of the substrate-binding cavity involved in hydrogen bonding with PEP, is well placed to react with E4P forming an imine linkage that is substantially protected from solvent water.

Superimposed saddle and ruffled distortions of the porphyrin in iodo(pyridine-N)(5,10,15,20-tetraphenylporphyrinato-kappa(4)N)rhodium(III) toluene solvate.

In the title compound, [RhI(C(44)H(28)N(4))(C(5)H(5)N)].C(7)H(8), the porphyrin ring experiences significant distortion from planarity (a saddle conformation with a superimposed ruffling), as a result of steric interactions with the 2,6-H atoms of the axial pyridine ligand. This also leads to a slight lengthening of the Rh-pyridine bond [Rh-N 2.102 (7) A] relative to those seen in other pyridine adducts of six-coordinate Rh(III). The metric parameters of the porphyrin core are comparable with those of related metalloporphyrin derivatives. No significant intermolecular interactions are observed between the metalloporphyrin and disordered solvate species.

Removing a hydrogen bond in the dimer interface of Escherichia coli manganese superoxide dismutase alters structure and reactivity.

Among manganese superoxide dismutases, residues His30 and Tyr174 are highly conserved, forming part of the substrate access funnel in the active site. These two residues are structurally linked by a strong hydrogen bond between His30 NE2 from one subunit and Tyr174 OH from the other subunit of the dimer, forming an important element that bridges the dimer interface. Mutation of either His30 or Tyr174 in Escherichia coli MnSOD reduces the superoxide dismutase activity to 30--40% of that of the wt enzyme, which is surprising, since Y174 is quite remote from the active site metal center. The 2.2 A resolution X-ray structure of H30A-MnSOD shows that removing the Tyr174-->His30 hydrogen bond from the acceptor side results in a significant displacement of the main-chain segment containing the Y174 residue, with local rearrangement of the protein. The 1.35 A resolution structure of Y174F-MnSOD shows that disruption of the same hydrogen bond from the donor side has much greater consequences, with reorientation of F174 having a domino effect on the neighboring residues, resulting in a major rearrangement of the dimer interface and flipping of the His30 ring. Spectroscopic studies on H30A, H30N, and Y174F mutants show that (like the previously characterized Y34F mutant of E. coli MnSOD) all lack the high pH transition of the wt enzyme. This observation supports assignment of the pH sensitivity of MnSOD to coordination of hydroxide ion at high pH rather than to ionization of the phenolic group of Y34. Thus, mutations near the active site, as in the Y34F mutant, as well as at remote positions, as in Y174F, similarly affect the metal reactivity and alter the effective pK(a) for hydroxide ion binding. These results imply that hydrogen bonding of the H30 imidazole N--H group plays a key role in substrate binding and catalysis.

Outer sphere mutations perturb metal reactivity in manganese superoxide dismutase.

Tyrosine 34 and glutamine 146 are highly conserved outer sphere residues in the mononuclear manganese active site of Escherichia coli manganese superoxide dismutase. Biochemical and spectroscopic characterization of site-directed mutants has allowed functional characterization of these residues in the wild-type (wt) enzyme. X-ray crystallographic analysis of three mutants (Y34F, Q146L, and Q146H) reveal subtle changes in the protein structures. The Y34A mutant, as well as the previously reported Y34F mutant, retained essentially the full superoxide dismutase activity of the wild-type enzyme, and the X-ray crystal structure of Y34F manganese superoxide dismutase shows that mutation of this strictly conserved residue has only minor effects on the positions of active site residues and the organized water in the substrate access funnel. Mutation of the outer sphere solvent pocket residue Q146 has more dramatic effects. The Q146E mutant is isolated as an apoprotein lacking dismutase activity. Q146L and Q146H mutants retain only 5-10% of the dismutase activity of the wild-type enzyme. The absorption and circular dichroism spectra of the Q146H mutant resemble corresponding data for the superoxide dismutase from a hyperthermophilic archaeon, Pyrobaculum aerophilum, which is active in both Mn and Fe forms. Interestingly, the iron-substituted Q146H protein also exhibits low dismutase activity, which increases at lower pH. Mutation of glutamine 146 disrupts the hydrogen-bonding network in the active site and has a greater effect on protein structure than does the Y34F mutant, with rearrangement of the tyrosine 34 and tryptophan 128 side chains.

The application of power ultrasound to the surface cleaning of silica and heavy mineral sands.

Power ultrasound may be used in the processing of minerals to clean their surfaces of oxidation products and fine coatings, mainly through the large, but very localised, forces produced by cavitation. Results of the application of power ultrasound to remove iron-rich coatings from the surfaces of silica sand used in glass making and to improve the electrostatic separation of mineral sand concentrates through lowering the resistivity of the conducting minerals (ilmenite and rutile) are presented. Parameters affecting ultrasonic cleaning, such as input power and levels of reagent addition, are discussed. In particular, we present data showing the relationship between power input and the particle size of surface coatings removed. This can be explained by the Derjaguin approximation for the energy of interaction between a sphere and a flat surface.

A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization.

Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.

RNA folding argues against a hot-start origin of life.

Opinion is strongly divided on whether life arose on earth under hot or cold conditions, the hot-start and cold-start scenarios, respectively. The origin of life close to deep thermal vents appears as the majority opinion among biologists, but there is considerable biochemical evidence that high temperatures are incompatible with an RNA world. To be functional, RNA has to fold into a three-dimensional structure. We report both theoretical and experimental results on RNA folding and show that (as expected) hot conditions strongly reduce RNA folding. The theoretical results come from energy-minimization calculations of the average extent of folding of RNA, mainly from 0-90 degrees C, for both random sequences and tRNA sequences. The experimental results are from circular-dichroism measurements of tRNA over a similar range of temperatures. The quantitative agreement between calculations and experiment is remarkable, even to the shape of the curves indicating the cooperative nature of RNA folding and unfolding. These results provide additional evidence for a lower temperature stage being necessary in the origin of life.

Crystal structure and iron-binding properties of the R210K mutant of the N-lobe of human lactoferrin: implications for iron release from transferrins.

Lactoferrin (Lf) and serum transferrin (Tf) combine high-affinity iron binding with an ability to release this iron at reduced pH. Lf, however, retains iron to significantly lower pH than Tf, giving the two proteins distinct functional roles. In this paper, we compared the iron-release profiles for human Lf, Tf, and their N-lobe half-molecules Lf(N) and Tf(N) and showed that half of the difference in iron retention at low pH ( approximately 1.3 pH units) results from interlobe interactions in Lf. To probe factors intrinsic to the N-lobes, we further examined the specific role of two basic residues that are proposed to form a pH-sensitive dilysine trigger for iron release in the N-lobe of Tf [Dewan, J. C., Mikami, B., Hirose, M., and Sacchettini, J. C. (1993) Biochemistry 32, 11963-11968] by mutating Arg 210 to Lys in the N-lobe half-molecule Lf(N). The R210K mutant was expressed, purified, and crystallized, and its crystal structure was determined and refined at 2.0-A resolution to a final R factor (R(free)) of 19.8% (25.0%). The structure showed that Lys 210 and Lys 301 in R210K do not form a dilysine interaction like that between Lys 206 and Lys 296 in human Tf. The R210K mutant retained iron to lower pH than Tf(N), consistent with the absence of the dilysine interaction but released iron at approximately 0.7 pH units higher than Lf(N). We conclude that (i) the ability of Lf to retain iron to significantly lower pH than Tf is due equally to interlobe interactions and to the absence in Lfs of an interaction analogous to the dilysine pair in Tfs, even when two lysines are present at the corresponding sequence positions, and (ii) an appropriately positioned basic residue (Arg 210 in human Lf) modulates iron release by inhibiting protonation of the N-lobe iron ligands, specifically His 253.

Redox reactions of neurotransmitters possibly involved in the progression of Parkinson's Disease.

In Parkinson's Disease the neuromelanin in the substania nigra is known to contain considerably increased amounts of iron suggesting the presence of free, unprotected iron ions during its formation. Iron(II) is known to interact with peroxide via Fenton's reaction producing OH-radicals or ferryl (Fe(IV)) species. This can readily oxidize the neurotransmitter dopamine to the neurotoxic 6-hydroxydopamine (6-OHDA) which is a strong reducing agent. The produced 6-OHDA is, in turn, able to reduce and possibly release iron, as iron(II), from the iron storage protein ferritin. This cycle of events could well explain the development of Parkinson's Disease due to a continuous production of cell damaging species. The contrasting behaviour of 6-OHDA with some other important catecholamines is discussed.

Structural changes accompanying pH-induced dissociation of the beta-lactoglobulin dimer.

We have used NMR spectroscopy to determine the three-dimensional (3D) structure, and to characterize the backbone dynamics, of a recombinant version of bovine beta-lactoglobulin (variant A) at pH 2. 6, where the protein is a monomer. The structure of this low-pH form of beta-lactoglobulin is very similar to that of a subunit within the dimer at pH 6.2. The root-mean-square deviation from the pH 6.2 (crystal) structure, calculated for backbone atoms of residues 6-160, is approximately 1.3 A. Differences arise from the orientation, with respect to the calyx, of the A-B and C-D loops, and of the flanking three-turn alpha-helix. The hydrophobic cavity within the calyx is retained at low pH. The E-F loop (residues 85-90), which moves to occlude the opening of the cavity over the pH range 7.2-6.2, is in the "closed" position at pH 2.6, and the side chain of Glu89 is buried. We also carried out measurements of (15)N T(1)s and T(2)s and (1)H-(15)N heteronuclear NOEs at pH 2.6 and 37 degrees C. Although the residues of the E-F loop (residues 86-89) have the highest crystallographic B-factors, the conformation of this loop is reasonably well defined by the NMR data, and its backbone is not especially mobile on the pico- to nanosecond time scale. Several residues (Ser21, Lys60, Ala67, Leu87, and Glu112) exhibit large ratios of T(1) to T(2), consistent with conformational exchange on a micro- to millisecond time scale. The positions of these residues in the 3D structure of beta-lactoglobulin are consistent with a role in modulating access to the hydrophobic cavity.

Functional implications of structural differences between variants A and B of bovine beta-lactoglobulin.

The structure of the trigonal crystal form of bovine beta-lactoglobulin variant B at pH 7.1 has been determined by X-ray diffraction methods at a resolution of 2.22 A and refined to values for R and Rfree of 0.239 and 0.286, respectively. By comparison with the structure of the trigonal crystal form of bovine beta-lactoglobulin variant A at pH 7.1, which was determined previously [Qin BY et al., 1998, Biochemistry 37:14014-14023], the structural consequences of the sequence differences D64G and V118A of variants A and B, respectively, have been investigated. Only minor differences in the core calyx structure occur. In the vicinity of the mutation site D64G on loop CD (residues 61-67), there are small changes in main-chain conformation, whereas the substitution V118A on beta-strand H is unaccompanied by changes in the surrounding structure, thereby creating a void volume and weakened hydrophobic interactions with a consequent loss of thermal stability relative to variant A. A conformational difference is found for the loop EF, implicated in the pH-dependent conformational change known as the Tanford transition, but it is not clear whether this reflects differences intrinsic to the variants in solution or differences in crystallization.

Structure of recombinant human lactoferrin expressed in Aspergillus awamori.

Human lactoferrin (hLf) has considerable potential as a therapeutic agent. Overexpression of hLf in the fungus Aspergillus awamori has resulted in the availability of very large quantities of this protein. Here, the three-dimensional structure of the recombinant hLf has been determined by X-ray crystallography at a resolution of 2.2 A. The final model, comprising 5339 protein atoms (residues 1-691, 294 solvent molecules, two Fe3+and two CO32- ions), gives an R factor of 0.181 (free R = 0.274) after refinement against 32231 reflections in the resolution range 10-2.2 A. Superposition of the recombinant hLf structure onto the native milk hLf structure shows a very high level of correspondence; the main-chain atoms for the entire polypeptide can be superimposed with an r.m.s. deviation of only 0.3 A and there are no significant differences in side-chain conformations or in the iron-binding sites. Dynamic properties, as measured by B-value distributions or iron-release kinetics, also agree closely. This shows that the structure of the protein is not affected by the mode of expression, the use of strain-improvement procedures or the changes in glycosylation due to the fungal system.