Individual isotopic specializations predict subsequent inter-individual variation in movement in a freshwater fish.

Despite many similarities and intuitive links between individual dietary specialization and behavioral inter-individual variation, these phenomena have been studied in isolation, and empirical data confirming relationships between these intraspecific variance sources are lacking. Here we use stable isotope analysis and acoustic telemetry to test the hypothesis that individual specialization in trophic (δ15 N) and littoral/pelagic prey reliance (δ13 C) covary with inter-individual variation in movement in a group of 34 free-swimming burbot (Lota lota). By performing stable isotope analysis on tissues with differing isotopic turnover rates (anal fin and dorsal muscle), in 24 lethally sampled burbot, we demonstrate that individual specialization in trophic niche (δ15 N) and littoral/pelagic prey reliance (δ13 C) occurred within the population. By performing stable isotope analysis on anal fins of a group of telemetry tagged burbot, we were able to show that interactions between trophic niche and littoral/pelagic prey reliance, explained a significant proportion of the subsequent between-individual variance in mean movement rates. These findings demonstrate an empirical connection between behavioral inter-individual variation and dietary specialization, thus providing a substantial expansion of our understanding of the wider ecological consequences of these interesting phenomena.

Temporal plasticity in thermal-habitat selection of burbot Lota lota a diel-migrating winter-specialist.

In this study, animal-borne telemetry with temperature sensors was coupled with extensive habitat temperature monitoring in a dimictic reservoir, to test the following hypotheses: behavioural thermoregulation occurs throughout the year and temperature selection varies on a diel and seasonal basis, in a winter-specialist diel-migrating fish. Burbot Lota lota demonstrated nightly behavioural thermoregulation throughout the year, with a large seasonal shift between selection for very cold temperatures (<2° C) optimal for reproduction during the spawning period and selection for warmer temperatures (12-14° C) optimal for hunting and feeding during non-reproductive periods. During daylight hours, while L. lota avoided habitats warmer than optimal for reproduction and feeding during the spawning and non-reproductive periods, respectively, active selection was limited to selection for 4-6° C habitat during the prespawning period. Although behavioural thermoregulation explained the night-time migration, behavioural thermoregulation only partially explained daytime behaviour, indicating that diel migration is best explained by a combination of factors. Thus, thermal-habitat selection was a good predictor of night-time habitat occupancy in a diel-migrating species. Together, these results show that thermal-habitat selection by fishes may be important throughout the year and a more seasonally plastic behaviour than previously recognized.

Prospective comparison of Fibroscan, King's score and liver biopsy for the assessment of cirrhosis in chronic hepatitis C infection.

Historically, liver biopsy (LB) was the sole method to evaluate the severity of hepatic fibrosis in patients with chronic hepatitis C infection. However, LB is expensive and associated with a risk of severe complications. Therefore, noninvasive tests have been developed to assess the severity of liver fibrosis. The accuracy of Fibroscan (FS) and King's score (KS) was evaluated individually and in combination using liver histology as the reference standard. One hundred and eighty-seven patients were identified who had undergone a biopsy with a diagnosis of chronic hepatitis C virus (HCV) mono-infection (HCV RNA-positive by RT-PCR), attending King's College Hospital (n = 88) or the Royal Free Hospital (n = 99) (London) between May 2006 and December 2007. Liver fibrosis was scored using the Ishak method; significant fibrosis was defined as Ishak fibrosis stage F3-F6, and cirrhosis defined as Ishak fibrosis F5-F6. The diagnostic accuracy of each test was assessed by area under receiver operator characteristic curves (AUROC). Median age was 49 years (43-54) and 115 (61%) were male. The AUROC for FS, KS and FS + KS for the diagnosis of Ishak F3-F6 were 0.83, 0.82 and 0.85, respectively and for the diagnosis of cirrhosis (>or=F5) were 0.96, 0.89 and 0.93, respectively. The negative predictive values for the diagnosis of cirrhosis using the optimal cut-off results for fibrsocan (10.05 kPa), KS (24.3) and the two combined (26.1) were 98%, 91% and 94%, respectively. The noninvasive markers and, particularly, FS were effective tests for the prediction of cirrhosis in chronic hepatitis C. Both KS and FS also had clinical utility for the prediction of Ishak fibrosis stages F3-F6.

A simple, noninvasive test for the diagnosis of liver fibrosis in patients with hepatitis C recurrence after liver transplantation.

Recurrent hepatitis C is a common cause of graft loss in patients undergoing liver transplantation, and serial protocol liver biopsies have been used to identify patients at risk of graft loss from rapid fibrosis progression. The aim of this study was to derive a simple noninvasive index to predict fibrosis in patients with recurrent hepatitis C post-transplant. A retrospective study was performed assessing serial liver biopsies for post-transplant chronic hepatitis C infection. One hundred eighty-five patients were included in the analysis; median age 53 years (interquartile range 48-59) and 140 (76%) were male. Liver histology showed 53 (29%) had Ishak fibrosis stages F0/F1, 31 (17%) had F2, 29 (16%) had F3, 19 (10%) had F4 and 53 (29%) had F5/F6. The London Transplant Centres' (LTC) score was derived combining aspartate aminotransferase (AST IU/L), time from liver transplant (TFLT months), international normalized ratio and platelets. Diagnostic accuracy of the LTC score was assessed using area under receiver-operating characteristic (ROC) curves. The area under the ROC curve for moderate fibrosis (F >or= 2) was 0.78 (95% CI, 0.70-0.86; P < 0.0001), for advanced fibrosis (F4-6) was 0.80 (95% CI, 0.72-0.87; P < 0.0001) and for cirrhosis was 0.80 (95% CI, 0.72-0.88; P < 0.0001). An optimal cut-off value of 6.3 distinguished patients with no or mild fibrosis (F

Do steatosis and steatohepatitis impact on sustained virological response (SVR) rates in patients receiving pegylated interferon and ribavirin for chronic hepatitis C infection?

The impact of steatosis on treatment response in chronic hepatitis C infection is controversial. The aim of this study was to determine whether steatosis +/- steatohepatitis on pre-treatment liver biopsy influenced sustained virological response (HCV RNA negative 6 months after completing therapy) in patients with chronic hepatitis C infection treated with pegylated interferon-alpha and ribavirin. One hundred and seventy-nine patients, median age 46 years (interquartile range 40-52), treated between 2001 and 2005. Histological evidence of steatosis was present in 93 patients (52%) and steatohepatitis in 33 patients (18%), 31 patients (17.3%) were cirrhotic. There were 106 (59%) responders, who were similar to non-responders in respect to gender, age, and pre-treatment ALT. On univariate analysis, infection with genotype 2 or 3 was associated with sustained virological response (odds ratio 6.5 (95% CI, 3.3-12.5); P < 0.0001), whereas cirrhosis and patient weight were associated with a reduced response (odds ratios 0.23 (95% CI, 0.11-0.48); P < 0.0001, and 0.97 (95% CI, 0.95-0.99); P < 0.01, respectively); steatohepatitis but not steatosis impacted on the likelihood of achieving sustained virological response (odds ratio 0.37 (95% CI, 0.17-0.77); P = 0.009, and P = 0.18, respectively). Multivariate analysis revealed that infection with genotype 1 or 4 (odds ratio 0.09 (95% CI, 0.03-0.32); P < 0.001) and pre-treatment weight (odds ratio 0.94 (95% CI, 0.90-0.98); P = 0.002) were the only variables associated independently with sustained virological response. In chronic hepatitis C infection, although steatosis was associated with steatohepatitis, neither was shown to affect sustained virological response, which was influenced by genotype, patient weight and the presence of cirrhosis.

The impact of hepatic steatosis on the natural history of chronic hepatitis C infection.

Since patients with hepatitis C virus (HCV) often have hepatic steatosis, this retrospective analysis aimed to assess whether steatosis influences fibrosis progression. We studied 112 HCV RNA positive subjects (median age 44, IQR 39-51 years), who had two liver biopsies performed (median biopsy interval 50, 34-74 months). Fibrosis was staged using the Ishak method and steatosis by the Kleiner system (<5% steatosis = S0, 5-33% = S1, 33-66% = S2, and >66% = S3). The subjects were untreated because they had mild fibrosis (n = 59), declined therapy (n = 48), or had co-existing disease precluding treatment (n = 5). On first liver biopsy, 60 (54%) had S0, 34 (30%) had S1, 12 (11%) had S2, and 6 (5%) had S3. Steatosis was associated with genotype 3, odds ratio 4.8 (95% CI 1.3-16.7, P = 0.02). Twenty-three patients (21%) had disease progression on the second biopsy, defined as an increase in Ishak score by > or =1 stage. On univariate analysis, fibrosis progression was associated with older age (P = 0.004), higher AST (P = 0.04), and steatosis (P = 0.005) but on multivariate analysis, only baseline steatosis was significant, odds ratio 14.3 (2.1-111.1, P = 0.006). Kaplan-Meier analysis demonstrated that steatosis impacted on time to progression to both significant fibrosis (Ishak > or =F3) and cirrhosis (Ishak F5-6) (P = 0.001 and P = 0.049, respectively). The finding that steatosis was significantly associated with fibrosis progression indicates that, independent of baseline fibrosis stage, patients should be considered for anti-viral treatment if steatosis is present. Furthermore, strategies to reduce steatosis may have a beneficial effect on fibrosis progression and, therefore, patient outcome.

Current and future management of chronic hepatitis C infection.

Current treatment for patients with chronic hepatitis C virus (HCV) infection consists of the combination of pegylated interferon and ribavirin. This treatment regimen achieves a sustained virological response, defined as undetectable HCV RNA 6 months after treatment cessation, in 50% of patients overall. There is therefore a need for new treatments to improve the sustained virological response rate and reduce the number of adverse effects associated with pegylated interferon and ribavirin. This review examines the current management of chronic HCV infection, including who is eligible for treatment, the optimum duration of treatment, and management of side effects. New drugs in development, such as HCV-specific protease inhibitors, polymerase inhibitors, immune modulators and ribavirin analogues, are outlined, and their role in the treatment armamentarium is discussed, whether used alone or in combination with existing treatments.

The prion folding problem.

Prion diseases are neurodegenerative disorders in which dramatic conformational change in the structure of the prion protein is the fundamental event. This structural transition involves the loss of substantial alpha-helical content and the acquisition of beta-sheet structure. A convergence of recent biological and structural studies argues that the mechanism underlying the prion diseases is truly unprecedented.

Digging for dead genes: an analysis of the characteristics of the pseudogene population in the Caenorhabditis elegans genome.

Pseudogenes are non-functioning copies of genes in genomic DNA, which may either result from reverse transcription from an mRNA transcript (processed pseudogenes) or from gene duplication and subsequent disablement (non-processed pseudogenes). As pseudogenes are apparently 'dead', they usually have a variety of obvious disablements (e.g., insertions, deletions, frameshifts and truncations) relative to their functioning homologs. We have derived an initial estimate of the size, distribution and characteristics of the pseudogene population in the Caenorhabditis elegans genome, performing a survey in 'molecular archaeology'. Corresponding to the 18 576 annotated proteins in the worm (i.e., in Wormpep18), we have found an estimated total of 2168 pseudogenes, about one for every eight genes. Few of these appear to be processed. Details of our pseudogene assignments are available from http://bioinfo.mbb.yale.edu/genome/worm/pseudogene. The population of pseudogenes differs significantly from that of genes in a number of respects: (i) pseudogenes are distributed unevenly across the genome relative to genes, with a disproportionate number on chromosome IV; (ii) the density of pseudogenes is higher on the arms of the chromosomes; (iii) the amino acid composition of pseudogenes is midway between that of genes and (translations of) random intergenic DNA, with enrichment of Phe, Ile, Leu and Lys, and depletion of Asp, Ala, Glu and Gly relative to the worm proteome; and (iv) the most common protein folds and families differ somewhat between genes and pseudogenes-whereas the most common fold found in the worm proteome is the immunoglobulin fold and the most common 'pseudofold' is the C-type lectin. In addition, the size of a gene family bears little overall relationship to the size of its corresponding pseudogene complement, indicating a highly dynamic genome. There are in fact a number of families associated with large populations of pseudogenes. For example, one family of seven-transmembrane receptors (represented by gene B0334.7) has one pseudogene for every four genes, and another uncharacterized family (represented by gene B0403.1) is approximately two-thirds pseudogenic. Furthermore, over a hundred apparent pseudogenic fragments do not have any obvious homologs in the worm.

Myeloma associated amyloidosis presenting as subacute liver failure.

Multiple myeloma related amyloidosis is rare and its presentation with subacute liver failure (SALF) has not been reported. A case is described of a 46 year old woman presenting with a six week history of nausea, abdominal pain, and jaundice. Routine tests failed to establish a cause. Computed tomography showed a small volume liver consistent with SALF. Emergency liver transplantation was not undertaken because of the suspicion of underlying malignancy. At necropsy, liver biopsy showed amyloid deposition and bone marrow biopsy showed multiple myeloma. Thus, amyloidosis should be added to the list of potential causes of SALF.

Crystal structure of manganese catalase from Lactobacillus plantarum.

BACKGROUND: Catalases are important antioxidant metalloenzymes that catalyze disproportionation of hydrogen peroxide, forming dioxygen and water. Two families of catalases are known, one having a heme cofactor, and the other, a structurally distinct family containing nonheme manganese. We have solved the structure of the mesophilic manganese catalase from Lactobacillus plantarum and its azide-inhibited complex. RESULTS: The crystal structure of the native enzyme has been solved at 1.8 A resolution by molecular replacement, and the azide complex of the native protein has been solved at 1.4 A resolution. The hexameric structure of the holoenzyme is stabilized by extensive intersubunit contacts, including a beta zipper and a structural calcium ion crosslinking neighboring subunits. Each subunit contains a dimanganese active site, accessed by a single substrate channel lined by charged residues. The manganese ions are linked by a mu1,3-bridging glutamate carboxylate and two mu-bridging solvent oxygens that electronically couple the metal centers. The active site region includes two residues (Arg147 and Glu178) that appear to be unique to the Lactobacillus plantarum catalase. CONCLUSIONS: A comparison of L. plantarum and T. thermophilus catalase structures reveals the existence of two distinct structural classes, differing in monomer design and the organization of their active sites, within the manganese catalase family. These differences have important implications for catalysis and may reflect distinct biological functions for the two enzymes, with the L. plantarum enzyme serving as a catalase, while the T. thermophilus enzyme may function as a catalase/peroxidase.

Evidence for post-translational changes in rat liver ferritin.

Analysis of rat liver isoferritins labelled by NaH14CO3 injection shows that acidic isoferritins decay exponentially, while activity in more basic isoferritins rises over 2-3 days. This suggests that isoferritins of low pI become more basic by post-translational modification, occurring over the whole life time of the protein.

The ferritins: molecular properties, iron storage function and cellular regulation.

The iron storage protein, ferritin, plays a key role in iron metabolism. Its ability to sequester the element gives ferritin the dual functions of iron detoxification and iron reserve. The importance of these functions is emphasised by ferritin's ubiquitous distribution among living species. Ferritin's three-dimensional structure is highly conserved. All ferritins have 24 protein subunits arranged in 432 symmetry to give a hollow shell with an 80 A diameter cavity capable of storing up to 4500 Fe(III) atoms as an inorganic complex. Subunits are folded as 4-helix bundles each having a fifth short helix at roughly 60 degrees to the bundle axis. Structural features of ferritins from humans, horse, bullfrog and bacteria are described: all have essentially the same architecture in spite of large variations in primary structure (amino acid sequence identities can be as low as 14%) and the presence in some bacterial ferritins of haem groups. Ferritin molecules isolated from vertebrates are composed of two types of subunit (H and L), whereas those from plants and bacteria contain only H-type chains, where 'H-type' is associated with the presence of centres catalysing the oxidation of two Fe(II) atoms. The similarity between the dinuclear iron centres of ferritin H-chains and those of ribonucleotide reductase and other proteins suggests a possible wider evolutionary linkage. A great deal of research effort is now concentrated on two aspects of ferritin: its functional mechanisms and its regulation. These form the major part of the review. Steps in iron storage within ferritin molecules consist of Fe(II) oxidation, Fe(III) migration and the nucleation and growth of the iron core mineral. H-chains are important for Fe(II) oxidation and L-chains assist in core formation. Iron mobilisation, relevant to ferritin's role as iron reserve, is also discussed. Translational regulation of mammalian ferritin synthesis in response to iron and the apparent links between iron and citrate metabolism through a single molecule with dual function are described. The molecule, when binding a [4Fe-4S] cluster, is a functioning (cytoplasmic) aconitase. When cellular iron is low, loss of the [4Fe-4S] cluster allows the molecule to bind to the 5'-untranslated region (5'-UTR) of the ferritin m-RNA and thus to repress translation. In this form it is known as the iron regulatory protein (IRP) and the stem-loop RNA structure to which it binds is the iron regulatory element (IRE). IREs are found in the 3'-UTR of the transferrin receptor and in the 5'-UTR of erythroid aminolaevulinic acid synthase, enabling tight co-ordination between cellular iron uptake and the synthesis of ferritin and haem. Degradation of ferritin could potentially lead to an increase in toxicity due to uncontrolled release of iron. Degradation within membrane-encapsulated "secondary lysosomes' may avoid this problem and this seems to be the origin of another form of storage iron known as haemosiderin. However, in certain pathological states, massive deposits of "haemosiderin' are found which do not arise directly from ferritin breakdown. Understanding the numerous inter-relationships between the various intracellular iron complexes presents a major challenge.

Functional studies on rat-liver isoferritins.

Rat-liver and horse-spleen isoferritins were obtained by preparative isoelectric focussing and several of these were fractionated further by sucrose density gradient centrifugation. H- and L-subunit compositions were also measured. Isoferritins were found to have neither a fixed iron content nor a unique subunit composition. In both species within a single isoferritin a small increase in the percentage of H subunit paralleled increasing iron content. Although in horse-spleen ferritin a similar correlation was found over the isoferritin profile as a whole, this was not generally true of rat-liver isoferritins, since iron distributions varied with the iron status of the animals. Rates of iron incorporation into isoapoferritins were measured in vitro and the distribution of 59Fe among rat liver isoferritins was measured at various times after injection of 59Fe. The data do not support the proposal that, in rat liver, L-rich isoferritins are the preferred iron-storage form.

Mössbauer spectroscopic investigation of structure-function relations in ferritins.

Ferritin plays an important role in iron metabolism and our aim is to understand the mechanisms by which iron is sequestered within its protein shell as the mineral ferrihydrite. We present Mössbauer spectroscopic data on recombinant human and horse spleen ferritin from which we draw the following conclusions: (1) that apoferritin catalyses Fe(II) oxidation as a first step in ferrihydrite deposition, (2) that the catalysis of Fe(II) oxidation is associated with residues situated within H chains, at the postulated 'ferroxidase centre' and not in the 3-fold inter-subunit channels previously suggested as the initial Fe(II) binding and oxidation site; (3) that both isolated Fe(III) and Fe(III) mu-oxo-bridged dimers found previously by Mössbauer spectroscopy to be intermediates in iron-core formation in horse spleen ferritin, are located on H chains; and (4) that these dimers form at ferroxidase centres. The importance of the ferroxidase centre is suggested by the conservation of its ligands in many ferritins from vertebrates, invertebrates and plants. Nevertheless iron-core formation does occur in those ferritins that lack ferroxidase centres even though the initial Fe(II) oxidation is relatively slow. We compare the early stages of core formation in such variants and in horse spleen ferritin in which only 10-15% of its chains are of the H type. We discuss our findings in relation to the physiological role of isoferritins in iron storage processes.

Physical, chemical and immunological properties of the bacterioferritins of Escherichia coli, Pseudomonas aeruginosa and Azotobacter vinelandii.

The 70-amino-acid-residue N-terminal sequence of the bacterioferritin (BFR) of Azotobacter vinelandii was determined and shown to be highly similar to the N-terminal sequences of the Escherichia coli and Nitrobacter winogradskyi bacterioferritins. Electrophoretic and immunological analyses further indicate that the bacterioferritins of E. coli, A. vinelandii and Pseudomonas aeruginosa are closely related. A novel, two-subunit assembly state that predominates over the 24-subunit form of BFR at low pH was demonstrated. The results indicate that the bacterioferritins form a family of proteins that are distinct from the ferritins of plants and animals.

Structure and composition of ferritin cores from pea seed (Pisum sativum).

Iron cores from native pea seed (Pisum sativum) ferritin have been analysed by electron microscopy and Mössbauer spectroscopy and shown to be amorphous. This correlates with their relatively high phosphate content (Fe: P = 2.83; 1800 Fe, 640 P atoms/molecule). Reconstituted cores obtained by adding iron (2000 Fe atoms/molecule) in the absence of phosphate to pea seed apoferritin were crystalline ferrihydrite. In vitro rates of formation of pea-seed ferritin iron cores were intermediate between those of recombinant human H-chain and horse spleen apoferritin and this may reflect the amino-acid residues of its ferroxidase and putative nucleation centres. The high phosphate content of pea-seed ferritin suggests that this molecule could be involved in both phosphorus and iron storage. The high phosphate concentration found within plastids, from which the molecules were isolated, is a possible source of the ferritin phosphate.

Analysis and classification of disulphide connectivity in proteins. The entropic effect of cross-linkage.

An analysis and a classification of protein disulphide connectivity in a set of distinct sequences are presented. We analyse the number of disulphides per sequence, the number of disulphides per residue and the length of disulphide cross-linked loops. Observed connectivities are classified according to the different possible types of arrangement. In addition, we classify disulphide connectivity by physical models describing the arrangement of multiple disulphides. Firstly, we consider whether the features of native connectivity arrangement are describable by the likelihood of diffusive contact in the unfolded state. This is referred to as the diffusion model, and was originated by Kauzmann. A second model, effectively the inverse of the diffusion model, describes native connectivity arrangement as dominated by the entropic stabilisation effect of cross-linkage. This is referred to as the entropic model. Additionally, we compare the distribution of disulphide cross-linked loops and of loops formed by disulphide-like contacts. For short sequences (less than about 75 residues) native connectivities tend to have entropically more-stabilising arrangement features, whilst for longer sequences (greater than about 200 residues) the diffusion model is appropriate. We introduce the concept of arrangement entropy as a measure of the complexity of a connectivity.

The disulphide beta-cross: from cystine geometry and clustering to classification of small disulphide-rich protein folds.

Small disulphide-rich protein folds (SDFs) tend to have less, regular secondary structure than larger protein folds and are thus problematic in protein structure taxonomy and prediction. We report regularities for disulphide-bridged beta-sheet and for cystine clustering that are particularly relevant to such proteins. The repertoire of cystine conformations results in preferences in disulphide distribution between/within beta-sheets. For example, disulphides seldom bridge between beta-sheets with antiparallel orientation for the flanking polypeptide segments, as the separations between packed sheets are such that the only rotamers that straddle them easily are those that generally require parallel orientation. A left-handed chirality preference is described for the intervening connection for disulphides bridging between berta-strands in different sheets in such a parallel orientation. Geometrical analysis of clusters of two cystine residues has shown that closely clustered cystine residues tend to have approximately orthogonal relative orientation. A positive orientation of this type is most often accommodated by a recurrent motif of disulphide-bridged beta-sheet that we call the disulphide beta-cross. The consensus features of this motif are described. It occurs in non-homologous proteins with a variety of folds, subsuming partial similarities previously noted by several other workers. Further examples are discussed, such as a two-cystine/two-beta-hairpin assembly common to hirudin and the three-fingered toxin folds. We suggest that the consensus features enable it to act as a good folding nucleus. We classify similar three-cystine arrangements that may be described as a ladder or stack, that tend to contain a disulphide beta-cross and that recur in folds that can otherwise be quite different. The preferences for disulphide-beta-sheet distribution and for cystine clusters contribute to an array of partial similarities for SDFs, many of which incorporate the disulphide beta-cross. It is suggested that SDF taxonomy cannot properly be considered without using both the relationship between clustered cystine residues and that between cystine residues and the regular secondary structures that they connect (here, we study beta in particular). The implications for SDF classification are demonstrated.

Reconstituted and native iron-cores of bacterioferritin and ferritin.

The structural and magnetic properties of the iron-cores of reconstituted horse spleen ferritin and Azotobacter vinelandii bacterioferritin have been investigated by high-resolution transmission electron microscopy, electron diffraction and Mossbauer spectroscopy. The structural properties of native horse spleen ferritin, native Az. vinelandii, and native and reconstituted Pseudomonas aeruginosa bacterioferritins have also been determined. Reconstitution in the absence of inorganic phosphate at pH 7.0 showed sigmoidal behaviour in each protein but was approximately 30% faster in initial rate for the Az. vinelandii protein when compared with horse spleen apoferritin. The presence of Zn2+ reduced the initial rate of Fe(II) oxidation in Az. vinelandii to 22% of the control rate. The iron-cores of the reconstituted bacterioferritins adopt defect ferrihydrite structures and are more highly ordered than their native counterparts, which are both amorphous. However, the blocking temperature for reconstituted Az. vinelandii (22.2 K) is almost identical to that for the native protein (20 K). Particle size measurements indicate that the reconstituted Az. vinelandii cores are smaller in median diameter than the native cores and this reduction in particle volume (V) offsets the increased magnetocrystalline contribution to the magnetic anisotropy constant (K) in such a way that the magnetic anisotropy barrier (KV), and hence the blocking temperature, is similar for both proteins. Reconstituted horse spleen ferritin exhibits a similar blocking temperature (38 K) to that determined for the native protein, although it is structurally more disordered. The possibility of introducing structural and compositional modifications in both horse ferritin and bacterioferritins by in-vitro reconstitution suggests that these proteins do not function primarily as a crystallochemical-specific interface for core development in vivo.