Fibril Width Research Articles

Orientated Bacterial Cellulose Culture Controlled by Liquid Substrate of Silicone Oil with Different Viscosity and Thickness

We report the effect of oxygen and viscoelasticity of culture interface on the orientation of bacterial cellulose (BC) fibril synthesized by Acetobacter xylimum (ATCC 53582) at a silicone oil/culture medium (liquid/liquid system) interface. In this work, we used the silicone oil with various kinematic viscosities, v ranging from 10 to 3000 centistokes (CS). We found that the birefringence, Δn as a measure of degree of orientation, fibril width, w, swelling degree, q, and tensile modulus, E, increased as increase the thickness and viscosity of silicone oil. However, fracture stress, σF and fracture strain, λF decreased with increase the silicone oil thickness and viscosity. Further, we also found that viscoelasticity of culture interface plays an important role to determine the orientation alignment of BC fibrils. Meanwhile, oxygen did not show significant influence on orientation of BC fibrils.

Molecular structural basis for polymorphism in Alzheimer's β-amyloid fibrils

We describe a full structural model for amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (Abeta(1-40)), based on numerous constraints from solid state NMR and electron microscopy. This model applies specifically to fibrils with a periodically twisted morphology, with twist period equal to 120 +/- 20 nm (defined as the distance between apparent minima in fibril width in negatively stained transmission electron microscope images). The structure has threefold symmetry about the fibril growth axis, implied by mass-per-length data and the observation of a single set of (13)C NMR signals. Comparison with a previously reported model for Abeta(1-40) fibrils with a qualitatively different, striated ribbon morphology reveals the molecular basis for polymorphism. At the molecular level, the 2 Abeta(1-40) fibril morphologies differ in overall symmetry (twofold vs. threefold), the conformation of non-beta-strand segments, and certain quaternary contacts. Both morphologies contain in-register parallel beta-sheets, constructed from nearly the same beta-strand segments. Because twisted and striated ribbon morphologies are also observed for amyloid fibrils formed by other polypeptides, such as the amylin peptide associated with type 2 diabetes, these structural variations may have general implications.

Ultrastructural Studies on the Collagen of the Marine Sponge Chondrosia reniformis Nardo

The ultrastructure of isolated fibrils of Chondrosia reniformis sponge collagen was investigated by collecting characteristic data, such as fibril thickness, width, D-band periodicity, and height modulation, using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Therefore an adapted pre-processing of the insoluble collagen into homogeneous suspensions using neutral buffer solutions was essential, and several purification steps have been developed. Fourier transform infrared reflection-absorption spectroscopy (FT-IRAS) of the purified sponge collagen showed remarkable analogy of peak positions and intensities with the spectra of fibrillar calf skin type I collagen, despite the diverse phylogenetic and evolutionary origin. The sponge collagen's morphology is compared with that of other fibrillar collagens, and the typical banding of the separated single fibrils is discussed by comparison of topographical data obtained using AFM and corresponding TEM investigations using common staining methods. As the TEM images of the negatively stained fibrils showed alternating dark and light bands, AFM revealed a characteristic periodicity of protrusions (overlap zones) followed by two equal interband regions (gap zones). AFM and TEM results were correlated and multiperiodicity in Chondrosia collagen's banding is demonstrated. The periodic dark bands observed in TEM images correspond directly to the periodic protrusions seen by AFM. As a result, we provide an improved, updated model of the collagen's structure and organization.

Annealing Prion Protein Amyloid Fibrils at High Temperature Results in Extension of a Proteinase K-resistant Core

Amyloids are highly ordered, rigid beta-sheet-rich structures that appear to have minimal dynamic flexibility in individual polypeptide chains. Here, we demonstrate that substantial conformational rearrangements occur within mature amyloid fibrils produced from full-length mammalian prion protein. The rearrangement results in a substantial extension of a proteinase K-resistant core and is accompanied by an increase in the beta-sheet-rich conformation. The conformational rearrangement was induced in the presence of low concentrations of Triton X-100 either by brief exposure to 80 degrees C or, with less efficacy, by prolonged incubation at 37 degrees C at pH 7.5 and is referred to here as "annealing." Upon annealing, amyloid fibrils acquired a proteinase K-resistant core identical to that found in bovine spongiform encephalopathy-specific scrapie-associated prion protein. Annealing was also observed when amyloid fibrils were exposed to high temperatures in the absence of detergent but in the presence of brain homogenate. These findings suggest that the amyloid fibrils exist in two conformationally distinct states that are separated by a high energy barrier and that yet unknown cellular cofactors may facilitate transition of the fibrils into thermodynamically more stable state. Our studies provide new insight into the complex behavior of prion polymerization and highlight the annealing process, a previously unknown step in the evolution of amyloid structures.

Higher-order Molecular Packing in Amyloid-like Fibrils Constructed with Linear Arrangements of Hydrophobic and Hydrogen-bonding Side-chains

Various mutants of the protein fragment, barnase module-1 (1-24) were investigated in order to reveal the structural principle of amyloid-like fibrils. By means of circular dichroism spectroscopy, X-ray diffraction, electron microscopy, and thioflavin T binding assay, we found that the molecules containing two beta-strands and an intervening turn structure are assembled to form a cross-beta structure. Stabilization by both the hydrophobic interactions and hydrogen bonding between the respective paired side-chains on the coupled beta-strands was essential for fibril formation. These two types of interaction can also arrange the corresponding residues in lines on both sheet surfaces of protofilaments with a cross-beta structure. This leads to the most probable fibril structure constructed with the line-matching interactions between protofilaments. Consideration of the geometrical symmetry resulted in our finding that a limited number of essential models for molecular packing in fibril structure are stable, which would rationally explain the occurrence of two or three morphologies from an identical molecular species. The ribbon-like fibrils exhibited striped texture along the axis, which was assigned to a stacked two-sheet repeat as a structural unit. The comprehensively proposed structural model, that is, the sheet-sheet interaction between left-handed cross-beta structures, results in a slightly right-handed twist of beta-sheet stacking, which reasonably elucidates the intrinsic sizes of the fibril width and its helical period along the fibril axis, as the bias in the orientation of the hydrogen-bonded beta-strand pair at the lateral edge is larger than that at the central protofilament.

Novel network morphology of poly(p-oxybenzoyl)

Polymerization of 4-acetoxybenzoic acid (ABA) with 3,5-diacetoxybenzoic acid (DABA) was examined to control the morphology of poly(p-oxybenzoyl) (POB). Polymerizations were carried out at a concentration of 1.0% in an aromatic solvent Therm S-1000® (mixture of dibenzyltoluene) at 320 °C. Polymerization of ABA yielded the POB fibrillar crystals, but the polymerization with DABA at a concentration in the feed (χf) of 0.10–0.15 afforded novel network structures comprised of spheres connected by fibrillar crystals. The diameter of the spheres prepared at χf of 0.15, which were 0.7 and 5.0 μm, showed bimodality. The network distance, fibril length, and fibril width were 6.1, 2.6, and 0.1 μm, respectively. They possessed high crystallinity. The network structure was formed as follows. Co-oligomers were first precipitated in the beginning of the polymerization by liquid–liquid phase separation to form the microdroplets. The fibrillar crystals were formed in the coalesced spheres by the crystallization of oligomers induced by the increase of molecular weight. The fibrillar crystals connecting the spheres gradually appeared owing to the shrinkage of the spheres. The fibrillar crystals grew from the surface of the spheres with the crystallization of homo-oligomers of 4-oxybenzoyl units, and finally the network structure was completed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1624–1634, 2005

Different propensity to form amyloid fibrils by two homologous proteins-Human stefins A and B: searching for an explanation.

By using ThT fluorescence, X-ray diffraction, and atomic force microscopy (AFM), it has been shown that human stefins A and B (subfamily A of cystatins) form amyloid fibrils. Both protein fibrils show the 4.7 A and 10 A reflections characteristic for cross beta-structure. Similar height of approximately 3 nm and longitudinal repeat of 25-27 nm were observed by AFM for both protein fibrils. Fibrils with a double height of 5.6 nm were only observed with stefin A. The fibril's width for stefin A fibrils, as observed by transmission electron microscopy (TEM), was in the same range as previously reported for stefin B (Zerovnik et al., Biochem Biophys Acta 2002;1594:1-5). The conditions needed to undergo fibrillation differ, though. The amyloid fibrils start to form at pH 5 for stefin B, whereas in stefin A, preheated sample has to be acidified to pH < 2.5. In both cases, adding TFE, seeding, and alignment in a strong magnetic field accelerate the fibril growth. Visual analysis of the three-dimensional structures of monomers and domain-swapped dimers suggests that major differences in stability of both homologues stem from arrangement of specific salt bridges, which fix alpha-helix (and the alpha-loop) to beta-sheet in stefin A monomeric and dimeric forms.

The bacterial linear motor of Spiroplasma melliferum BC3: from single molecules to swimming cells.

Spiroplasma melliferum BC3 are wall-less bacteria with internal cytoskeletons. Spiroplasma, Mycoplasma and Acholeplasma belong to the Mollicutes, which represent the smallest, simplest and minimal free-living and self-replicating forms of life. The Mollicutes are motile and chemotactic. Spiroplasma cells are, in addition, helical in shape. Based on data merging, obtained by video dark-field light microscopy of live, swimming helical Spiroplasma cells and by cryoelectron microscopy, unravelling the subcellular structure and molecular organization of the cytoskeleton, we propose a functional model in which the cytoskeleton also acts as a bacterial linear motor enabling and controlling both dynamic helicity and swimming. The cytoskeleton is a flat, monolayered ribbon constructed from seven contractile fibrils (generators) capable of changing their length differentially in a co-ordinated manner. The individual, flat, paired fibrils can be viewed as chains of tetramers approximately 100 A in diameter composed of 59 kDa monomers. The cytoskeletal ribbon is attached to the inner surface of the cell membrane (but is not an integral part of it) and follows the shortest helical line on the coiled cellular tube. We show that Spiroplasma cells can be regarded, at least in some states, as near-perfect dynamic helical tubes. Thus, the analysis of experimental data is reduced to a geometrical problem. The proposed model is based on simple structural elements and functional assumptions: rigid circular rings are threaded on a flexible, helical centreline. The rings maintain their circularity and normality to the centreline at all helical states. An array of peripheral, equidistant axial lines forms a regular cylindrical grid (membrane), by crossing the lines bounding the rings. The axial and peripheral spacing correspond to the tetramer diameter and fibril width (100 A) respectively. Based on electron microscopy data, we assign seven of the axial grid lines in the model to function as contractile generators. The generators are clustered along the shortest helical paths on the cellular coil. In the model, the shortest generator coincides with the shortest helical line. The rest, progressively longer, six generators follow to the right or to the left of the shortest generator in order to generate the maximal range of lengths. A rubbery membrane is stretched over (or represented by) the three-dimensional grid to form a continuous tube. Co-ordinated, differential length changes of the generators induce the membranal cylinder to coil and uncoil reversibly. The switch of helical sense requires equalization of the generators' length, forming a straight cylindrical tube with straight generators. The helical parameters of the cell population, obtained by light microscopy, constitute several subpopulations related, most probably, to cell size and age. The range of molecular dimensions in the active cytoskeleton inferred from light microscopy and modelling agrees with data obtained by direct measurements of subunit images on electron micrographs, scanning transmission electron microscopy (STEM) and diffraction analysis of isolated ribbons. Swimming motility and chemotactic responses are carried out by one or a combination of the following: (i). reciprocating helical extension and compression ('breathing'); (ii). propagation of a deformation (kink) along the helical path; (iii). propagation of a reversal of the helical sense along the cell body; and (iv). irregular flexing and twitching, which is functionally equivalent to standard bacterial tumbling. Here, we analyse in detail only the first case (from which all the rest are derived), including switching of the helical sense.

Hierarchical self-assembly of chiral rod-like molecules as a model for peptide beta -sheet tapes, ribbons, fibrils, and fibers.

A generic statistical mechanical model is presented for the self-assembly of chiral rod-like units, such as beta-sheet-forming peptides, into helical tapes, which with increasing concentration associate into twisted ribbons (double tapes), fibrils (twisted stacks of ribbons), and fibers (entwined fibrils). The finite fibril width and helicity is shown to stem from a competition between the free energy gain from attraction between ribbons and the penalty because of elastic distortion of the intrinsically twisted ribbons on incorporation into a growing fibril. Fibers are stabilized similarly. The behavior of two rationally designed 11-aa residue peptides, P(11)-I and P(11)-II, is illustrative of the proposed scheme. P(11)-I and P(11)-II are designed to adopt the beta-strand conformation and to self-assemble in one dimension to form antiparallel beta-sheet tapes, ribbons, fibrils, and fibers in well-defined solution conditions. The energetic parameters governing self-assembly have been estimated from the experimental data using the model. The 8-nm-wide fibrils consist of eight tapes, are extremely robust (scission energy approximately 200 k(B)T), and sufficiently rigid (persistence length l(fibril) approximately 20-70 microm) to form nematic solutions at peptide concentration c approximately 0.9 mM (volume fraction approximately 0.0009 vol/vol), which convert to self-supporting nematic gels at c > 4 mM. More generally, these observations provide a new insight into the generic self-assembling properties of beta-sheet-forming peptides and shed new light on the factors governing the structures and stability of pathological amyloid fibrils in vivo. The model also provides a prescription of routes to novel macromolecules based on a variety of self-assembling chiral units, and protocols for extraction of the associated energy changes.

The fibril structure of type V collagen triple-helical domain

Although the triple-helical structure of fibrillar collagen is regarded in general as being quite similar, each type of collagen molecule has inherent characteristics in the triple-helical domain. Few studies have ever been performed in terms of the aggregate structure of the triple-helical domain of fibrillar collagen. Reconstituted aggregates from the purified triple-helical domain of each type of fibrillar collagen might amplify the subtle differences in the structural characteristics of each type of collagen molecule. In this study, the reconstituted aggregate structure of pepsin-treated type V collagen (type Vp collagen), that is, virtually its triple-helical domain was characterized by transmission electron microscopy. Pepsin-treated type I (type Ip) and type II (type IIp) collagen were compared with type Vp collagen. Unique features of the aggregate structure of the triple-helical domain of the type V collagen can be summarized as follows:1.Type Vp collagen formed fibrils with the D-periodic banding pattern. The banded type Vp fibrils appeared to be of a loosely twisted ribbon-like structure. The average thickness of type Vp collagen fibrils with the banding pattern was significantly smaller than those reconstituted from types Ip and IIp collagen.2.The width of the type Vp collagen fibrils was not affected under the conditions where the D-periodic banded fibrils were formed; the conditions being incubation temperature, protein concentration, and NaCl concentration.3.Type Vp collagen fibrils had little branching and merging. Furthermore, the type Vp collagen fibrils did not bind to each other. On the contrary, type Ip collagen fibrils were often bound to each other and had many branching and merging.These results suggested that the lateral packing of the triple-helical domain of type V collagen is determined by its molecular structure. The characteristics of type Vp collagen fibrils might be explained by their characteristic amino acid composition. A significant feature of the triple-helical domain of type V collagen is the high content of glycosylated hydroxylysine residues. Molecular model building of the collagenous structure suggests that a change in surface roughness is conspicuous by incorporating the glycosylated hydroxylysine residues. More than a ten-fold content of bulky glycosylated hydroxylysine residues in type V collagen compared to that of type I might have a significant influence on both the intermolecular and interfibrillar interactions of the triple-helical domain of type V collagen molecule.

Investigation of the nanofibrils of silk fibers

Silk from 3-molted, 4-molted and sex-limited Bombyx mori, Antheraea pernyi and Antheraea yamamai have been investigated using Atomic Force Microscopy and Low Voltage High Resolution Scanning Electron Microscopy. Nanofibrils, bundles of nanofibrils, helical features and a layered structure with a cross angle between nanofibrils in different layers were observed for all silks. Similar log-normal distributions of fibril widths were obtained from all silks with the geometric mean fibril widths covering the range of 90–170nm. There is no correlation of the fibril width with the fiber size from different types of silkworm. Similar normal distributions of cross angles were observed in 30% of the images with the arithmetic means covering the range of 30–50°. There is an apparent correlation of cross angle with fiber size. The larger fibers for which the crystals are primarily alanine exhibit a greater average cross angle, 46°, than do those of the smaller fibers for which the crystals are primarily alanine and glycine, 36°. Initial wide angle X-ray diffraction measurements on a single fiber of A. pernyi are consistent with the fraction of fibrils at different cross angles being 28%. A simplified computer calculation method and molecular modeling were used in a search for packing angles which minimize the interaction energy of packing between beta sheets. Initial results revealed no definitive evidence of epitaxy to account for the cross angles. It is proposed that a multifibrillar fiber offers a number of mechanical advantages over a solid fiber with the same cross sectional area.

Relationship between Suspension Properties and Fibril Structure of Disintegrated Bacterial Cellulose.

A new method evaluating the fibril width and length of disintegrated bacterial cellulose was developed using optical and rheological analysis. During the early stages of the disintegration process, the bacterial cellulose particles formed loose fibrous aggregates, followed by cutting of the disintegrated fibrils that produced short fibrils. On the other hand, the fibril width decreased steadily throughout disintegration. The relationships between fibril structure and suspension properties were analyzed by a multiple regression method. The thinner and longer the disintegrated bacterial cellulose fibrils were, the higher the viscosity and water-holding capacity became.

Studies of Structure and Morphology Development During the Heat-Draw Process of Nylon 66 Fiber by Synchrotron X-ray Diffraction and Scattering Techniques

Online studies of structure and morphology development during continuous drawing of a nylon 66 fiber at different temperatures were carried out using synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. From the two-dimensional (2D) WAXD measurement, unit-cell parameters were determined. The results confirm that the triclinic cell structure persists above the Brill transition temperature (about 443 K). With increasing temperature, the unit-cell dimension a (dominated by hydrogen bonding) remains almost unchanged, while b increases and c decreases (both show a step-change at 403 K, prior to the Brill transition). The constant value of a agrees with the argument that the hydrogen bonding is relatively immobile at high temperatures prior to melting. The step-changes in b and c suggest that a premelting process of small (or defective) crystals precedes the Brill transition. As a result, the anisotropic thermal expansion of the surviving larger crystals results in a step-change behavior. This hypothesis is consistent with the crystal density data as well as the morphology evaluation by SAXS. Several dimensions were extracted from the 2D SAXS data: lamellar crystal and amorphous thicknesses (along the fiber) determined by the correlation function method, and crystal fibril width (perpendicular to the fiber) determined by the Porod analysis. These results also indicate that drawing annihilates small crystals, but the strain effect is much less than the temperature effect.

Characterization of Langmuir-Blodgett films of parent polyaniline

Conducting Langmuir-Blodgett (LB) films have been fabricated from parent polyaniline (PAni) which was doped with functionalized acids. In order to optimize experimental conditions for the formation of stable Langmuir monolayers and their subsequent transfer onto solid substrates, PAni was dissolved in ten different combinations of chloroform solutions. Use was made of camphor sulfonic acid, dodecyl benzene sulfonic acid, and toluenesulfonic acid, and of the solvents N-methyl pyrrolidine and m-cresol as processing agents. Because acidic subphases have been employed, as-deposited LB films were already doped, which was confirmed by the appearance of a polaronic band in the UV-Vis absorption spectra. The absorbance peak increases with the number of deposited layers indicating that a suitable multilayer buildup is accomplished. When analysed by atomic force microscopy, PAni LB films show a fibrillar structure with the fibril width ranging from ≈60 to 160 nm.

Effect of monovalent anions on type I collagen fibrillogenesis in vitro

The effect of a set of monovalent anions with different preferential binding to proteins (C1 −, Br −, I −, SCN −) on the kinetics of type I collagen fibrillogenesis was studied. Evidences obtained from turbidity-time curves and the Arrenhius plot suggested the presence of a conformational change prior to fibril formation, also supported by previous data available in the literature. A model of the initial steps of collagen assembly was proposed that could explain the action of the monovalent anions studied and other cosolvents on fibrillogenesis. Analysis of fibril width and 1-anilinonaphthalene-8-sulfonic acid (ANS) binding to collagen pointed to the presence of a nucleation process within the lag time

Structure of rat tail tendon collagen examined by atomic force microscope.

The Atomic Force Microscope (AFM) was used to inspect collagen fibrils deposited on mica sheets at different fibrillogenesis times. Collagen was obtained from rat tail tendon fibers. Various fibril forms were observed, together with the characteristic periodic intra-fibril structure (D-bands). The fibril thickness, width, D-band periodicity and depth were measured and the statistical distribution of these parameters at 1, 2, 5, 10 and 15 days of in vitro fibril formation time was calculated. The fibrils showed an increasing size with time, but the band interval measure remained stable. The band depth, after an initial increase, exhibited a relative steadiness. The results indicate that AFM offers, at low resolution, images qualitatively similar to those obtained with electron microscopy, but with less manipulation of the sample. A quantitative evaluation of collagen structural features in the nanometer scale is made possible by AFM.

An electron microscopic study of collagen fibril structure after lithium treatment—II. The effects of low lithium dose and short treatment on mouse skin collagen

The structure of mouse skin collagen fibrils, after treatment with lithium chloride at a dose of 0.7 meq/kg of body weight, was studied by electron microscopy. Animals were sacrificed 1-day, 1-, 2- and 6-months after the end of 30 consecutive days experimental period. Fibrils in disarray interspersed with normal ones were seen, although there were areas where the normal parallel packing of fibrils was completely replaced by a random arrangement. In some regions this packing was interrupted by fibrils forming a ‘hairpin loop’ and in some others helical twisting was apparent. Lithium treated collagen fibrils had a marked decrease in mean diameter compared to normal with a high variability in width. Clusters of abnormal fibrils were found when viewed in cross-sections, constituted approximately 10% of the whole population with an irregular outline. A shorter experimental period (7 days) leads to the same features in collagen disorganization as with the longer experimental period (30 periods). However, in short lithium treatment, there is no high variability in fibril width and although fibrils are smaller than the control, the decrease in mean diameter is not so pronounced as with longer treatment. In general, fibril diameter becomes altered progressively with experimental time. Lower dose, 0.3 meq Li/kg, in short treatment (7 days), leads to a normal collagen organization although in some areas fibril twisting is observed. Fibril diameter is not considerably affected.

Effects of phosphoprotein on collagen fibril formation in vitro

Transmission electron microscopy showed that when either dentinal phosphoprotein or calcium-treated phosphoprotein or phosvitin were introduced during type I collagen fibrillogenesis the fibrils formed were significantly wider and the cross-banding was more distinct than in the absence of phosphoprotein. The collagen fibril width also increased with increasing concentrations of these molecules. When either bovine serum albumin (BSA) or dephosphorylated dentine phosphoprotein were used, no differences in the fibril characteristics were seen when compared to the controls that contained no phosphoprotein or BSA. When these dialysed matrices were placed into mineralizing solutions, no mineral was observed in any of the samples.

Light and electron microscopic abnormalities in diastrophic dysplasia growth cartilage.

Light and electron microscopic studies of diastrophic dysplasia iliac crest growth cartilage performed on five occasions in two patients from 1 to 10 years of age reveal extensive cell and matrix abnormalities at each time period. Light microscopy shows atypical chondrocytes with extreme variation in size and shape, and premature cytoplasmic degeneration, and formation of target ghost cells. Prominent, densely staining fibrotic foci are present throughout the cartilage. Ultrastructure reveals some structurally intact chondrocytes with a single large fat inclusion, slightly dilated rough endoplasmic reticulum, and abundant glycogen. As early as 1 year of age cystic degeneration of chondrocyte cytoplasm is evident with indistinct organelles seen. The cartilage matrix demonstrates a general increase in fibrous tissue as well as the fibrotic foci. The collagen in these foci is remarkably abnormal. It is composed of short, extremely broad fibrils ranging from 150 to 950 nm in width which are separated at their terminal ends but fused to each other centrally in random fashion. On cross-section there are very few round fibrils but rather a marked irregularity in shape giving the appearance of having fibrils randomly added to others to form enlarged nonuniform fibril aggregates. On longitudinal sectioning, regular cross-banding across the entire fibril width is seen but fibril splitting and aggregation are highly irregular.(ABSTRACT TRUNCATED AT 250 WORDS)

A model for the fibril structure of normal-polarity solar prominences

A normal-polarity prominence is modelled as a series of cool fibrils set in the hotter corona. Equations of magnetostatic equilibrium are solved and each fibril corresponds to a dip in the mgnetic field. The ratio of fibril width to interfibril spacing is dependent on the prominence-coronal temperature ratio and the ratio of plasma to magnetic pressure. The prominence mass is found to depend on the square of the magnetic field strength. When variations along the prominence are allowed in addition to those across the prominence, an apparently random pattern of fibrils results.