Prediction of the absolute aggregation rates of amyloidogenic polypeptide chains

Protein aggregation is associated with a variety of pathological conditions, including Alzheimer's and Creutzfeldt-Jakob diseases and type II diabetes. Such degenerative disorders result from the conversion of the normal soluble state of specific proteins into aggregated states that can ultimately form the characteristic amyloid fibrils found in diseased tissue. Under appropriate conditions it appears that many, perhaps all, proteins can be converted in vitro into amyloid fibrils. The aggregation propensities of different polypeptide chains have, however, been observed to vary substantially. Here, we describe an approach that uses the knowledge of the amino acid sequence and of the experimental conditions to reproduce, with a correlation coefficient of 0.92 and over five orders of magnitude, the in vitro aggregation rates of a wide range of unstructured peptides and proteins. These results indicate that the formation of protein aggregates can be rationalised to a considerable extent in terms of simple physico-chemical parameters that describe the properties of polypeptide chains and their environment.     

Amyloid fibril formation from crude protein mixtures

Amyloid fibrils have potential as bionanomaterials. A bottleneck in their commercial use is the cost of the highly purified protein typically needed as a starting material. Thus, an understanding of the role of heterogeneity in the mixtures from which amyloid fibrils are formed may inform production of these structures from readily available impure starting materials. Insulin, a very well understood amyloid-forming protein, was modified by various reagents to explore whether amyloid fibrils could still form from a heterogeneous mixture of insulin derivatives. Aggregates were characterized by thioflavin T fluorescence and transmission electron microscopy. Using acetylation, reduction carboxymethylation, reduction pyridylethylation, trypsin digestion and chymotrypsin digestion, it was shown that amyloid fibrils can form from heterogeneous mixtures of modified insulin. The modifications changed both the rate of reaction and the yield of the final product, but led to fibrillar structures, some with interesting morphologies. Well defined, long, unbranched fibrils were observed in the crude reduced carboxymethylated insulin mixture and the crude reduced pyridylethylated insulin revealed the formation of "wavy" fibrils, compared with the straighter native insulin amyloid fibrils. Although trypsin digestion inhibited fibrils formation, chymotrypsin digestion of insulin produced a mixture of long and short fibrils under the same conditions. We conclude that amyloid fibrils may be successfully formed from heterogeneous mixtures and, further, that chemical modification may provide a simple means of manipulating protein fibril assembly for use in bionanotechnological applications, enabling some design of overall morphology in the bottom-up assembly of higher order protein structures from amyloid fibrils.     

The impact of solubility and electrostatics on fibril formation by the H3 and H4 histones

The goal of this study was to examine fibril formation by the heterodimeric eukaryotic histones (H2A-H2B and H3-H4) and homodimeric archaeal histones (hMfB and hPyA1). The histone fold dimerization motif is an obligatorily domain-swapped structure comprised of two fused helix:β-loop:helix motifs. Domain swapping has been proposed as a mechanism for the evolution of protein oligomers as well as a means to form precursors in the formation of amyloid-like fibrils. Despite sharing a common fold, the eukaryotic histones of the core nucleosome and archaeal histones fold by kinetic mechanisms of differing complexity with transient population of partially folded monomeric and/or dimeric species. No relationship was apparent between fibrillation propensity and equilibrium stability or population of kinetic intermediates. Only H3 and H4, as isolated monomers and as a heterodimer, readily formed fibrils at room temperature, and this propensity correlates with the significantly lower solubility of these polypeptides. The fibrils were characterized by ThT fluorescence, FTIR, and far-UV CD spectroscopies and electron microscopy. The helical histone fold comprises the protease-resistant core of the fibrils, with little or no protease protection of the poorly structured N-terminal tails. The highly charged tails inhibit fibrillation through electrostatic repulsion. Kinetic studies indicate that H3 and H4 form a co-fibril, with simultaneous incorporation of both histones. The potential impact of H3 and H4 fibrillation on the cytotoxicity of extracellular histones and α-synuclein-mediated neurotoxicity and fibrillation is considered.     

Identification of β-aggregate sites in protein chains

The problem of amyloidoses is pressing and have recently attracted special attention throughout the world because of epidemics of prion diseases such as mad cow disease and human Creutzfeldt-Jacob disease. These diseases result from the conversion of a native protein or peptide into a highly stable pathological form. Molecules having a pathological conformation aggregate to form amyloid fibrils, capable of unlimited growth. It is important to study the molecular mechanisms of prion diseases and to identify the protein regions responsible for their development. The review considers theoretical and experimental works focusing on the formation of amyloid fibrils.     

A partially structured region of a largely unstructured protein, Plasmodium falciparum merozoite surface protein 2 (MSP2), forms amyloid-like fibrils.

Merozoite surface protein 2 (MSP2) from the human malaria parasite Plasmodium falciparum is expressed as a GPI-anchored protein on the merozoite surface. It has been implicated in the process of erythrocyte invasion and is a leading vaccine candidate. MSP2 is an intrinsically unstructured protein (IUP), and recombinant MSP2 forms amyloid-like fibrils upon storage. We have examined synthetic peptides corresponding to sequences in the conserved N-terminal region of MSP2 for the presence of local structure and the ability to form fibrils related to those formed by full-length MSP2. In a 25-residue peptide corresponding to the entire N-terminal region of mature MSP2, structures calculated from NMR data show the presence of nascent helical and turn-like structures. An 8-residue peptide from the central region of the N-terminal domain (residues 8-15) also formed a turn-like structure. Both peptides formed fibrils that were similar but not identical to the amyloid-like fibrils formed by full-length MSP2. Notably, the fibrils formed by the peptides bound both Congo Red and Thioflavin T, whereas the fibrils formed by full-length MSP2 bound only Congo Red. The propensity of peptides from the N-terminal conserved region of MSP2 to form amyloid-like fibrils makes it likely that this region contributes to fibril formation by the full-length protein. Thus, in contrast to the more common pathway of amyloid formation by structured proteins, which proceeds via partially unfolded intermediates that then undergo beta-aggregation, MSP2 is an example of a largely unstructured protein with at least one small structured region that has an important role in fibril formation.     

The Familial British Dementia Mutation Promotes Formation of Neurotoxic Cystine Cross-linked Amyloid Bri (ABri) Oligomers

Familial British dementia (FBD) is an inherited neurodegenerative disease believed to result from a mutation in the BRI2 gene. Post-translational processing of wild type BRI2 and FBD-BRI2 result in the production of a 23-residue long Bri peptide and a 34-amino acid long ABri peptide, respectively, and ABri is found deposited in the brains of individuals with FBD. Similarities in the neuropathology and clinical presentation shared by FBD and Alzheimer disease (AD) have led some to suggest that ABri and the AD-associated amyloid β-protein (Aβ) are molecular equivalents that trigger analogous pathogenic cascades. But the sequences and innate properties of ABri and Aβ are quite different, notably ABri contains two cysteine residues that can form disulfide bonds. Thus we sought to determine whether ABri was neurotoxic and if this activity was regulated by oxidation and/or aggregation. Crucially, the type of oxidative cross-linking dramatically influenced both ABri aggregation and toxicity. Cyclization of Bri and ABri resulted in production of biologically inert monomers that showed no propensity to assemble, whereas reduced ABri and reduced Bri aggregated forming thioflavin T-positive amyloid fibrils that lacked significant toxic activity. ABri was more prone to form inter-molecular disulfide bonds than Bri and the formation of covalently stabilized ABri oligomers was associated with toxicity. These results suggest that extension of the C-terminal of Bri causes a shift in the type of disulfide bonds formed and that structures built from covalently cross-linked oligomers can interact with neurons and compromise their function and viability.     

Effects of salt concentration on association of the amyloid protofilaments of hen egg white lysozyme studied by time-resolved neutron scattering

Various proteins have been shown to form various aggregated structures including the filamentous aggregates known as amyloid fibrils depending on the solution conditions. Hen egg white lysozyme (HEWL) is one of the proteins that form the amyloid fibrils. To gain insight into the mechanism of this polymorphism of the aggregated structures, we employed a model system consisting of HEWL, pure water, and ethanol, and investigated the kinetic process of the fibril formation in various salt concentrations with time-resolved neutron scattering. It was shown that by addition of NaCl in a range between 0.3 mM and 1.0 mM to HEWL solution in 90% ethanol, gelation occurred, and this gelation proceeded through a two-step process: the lateral association of the protofilaments, followed by the cross-linking of these fibrils formed. Both the structures of the fibrils and the rate of the gelation depended on NaCl concentration. The average structures of the fibrils formed at 1.0 mM NaCl were characterized by the radius of gyration of their cross-section (45.9(+/-0.4)A) and the number of the protofilaments within the fibril (4.10(+/-0.12)), corresponding to the mature amyloid fibrils. A range of intermediate structures was formed below 1 mM NaCl. Above 2 mM NaCl, precipitation occurred because of the formation of amorphous aggregates. Here the branch point to the formation of the mature amyloid fibrils or to the amorphous aggregates was after the formation of the protofilaments. Sensitivity of the aggregated structures to salt concentration suggests that electrostatic interaction plays an essential role in the formation of these structures. The structural diversity both in the fibrils and the aggregated structures of the fibrils can be interpreted in terms of the difference in the degree of the electrostatic shielding at different salt concentrations.     

Role of aggregation conditions in structure, stability, and toxicity of intermediates in the Abeta fibril formation pathway

beta-amyloid peptide (Abeta) is one of the main protein components of senile plaques associated with Alzheimer's disease (AD). Abeta readily aggregates to forms fibrils and other aggregated species that have been shown to be toxic in a number of studies. In particular, soluble oligomeric forms are closely related to neurotoxicity. However, the relationship between neurotoxicity and the size of Abeta aggregates or oligomers is still under investigation. In this article, we show that different Abeta incubation conditions in vitro can affect the rate of Abeta fibril formation, the conformation and stability of intermediates in the aggregation pathway, and toxicity of aggregated species formed. When gently agitated, Abeta aggregates faster than Abeta prepared under quiescent conditions, forming fibrils. The morphology of fibrils formed at the end of aggregation with or without agitation, as observed in electron micrographs, is somewhat different. Interestingly, intermediates or oligomers formed during Abeta aggregation differ greatly under agitated and quiescent conditions. Unfolding studies in guanidine hydrochloride indicate that fibrils formed under quiescent conditions are more stable to unfolding in detergent than aggregation associated oligomers or Abeta fibrils formed with agitation. In addition, Abeta fibrils formed under quiescent conditions were less toxic to differentiated SH-SY5Y cells than the Abeta aggregation associated oligomers or fibrils formed with agitation. These results highlight differences between Abeta aggregation intermediates formed under different conditions and provide insight into the structure and stability of toxic Abeta oligomers.     

The Disulfide Bond,but Not Zinc or Dimerization,Controls Initiation and Seeded Growth in Amyotrophic Lateral Sclerosis-linked Cu,Zn Superoxide Dismutase (SOD1) Fibrillation

Aggregation of copper-zinc superoxide dismutase (SOD1) is a defining feature of familial ALS caused by inherited mutations in the sod1 gene, and misfolded and aggregated forms of wild-type SOD1 are found in both sporadic and familial ALS cases. Mature SOD1 owes its exceptional stability to a number of post-translational modifications as follows: formation of the intramolecular disulfide bond, binding of copper and zinc, and dimerization. Loss of stability due to the failure to acquire one or more of these modifications is proposed to lead to aggregation in vivo. Previously, we showed that the presence of apo-, disulfide-reduced SOD1, the most immature form of SOD1, results in initiation of fibrillation of more mature forms that have an intact Cys-57–Cys-146 disulfide bond and are partially metallated. In this study, we examine the ability of each of the above post-translational modifications to modulate fibril initiation and seeded growth. Cobalt or zinc binding, despite conferring great structural stability, neither inhibits the initiation propensity of disulfide-reduced SOD1 nor consistently protects disulfide-oxidized SOD1 from being recruited into growing fibrils across wild-type and a number of ALS mutants. In contrast, reduction of the disulfide bond, known to be necessary for fibril initiation, also allows for faster recruitment during seeded amyloid growth. These results identify separate factors that differently influence seeded growth and initiation and indicate a lack of correlation between the overall thermodynamic stability of partially mature SOD1 states and their ability to initiate fibrillation or be recruited by a growing fibril.     

Amyloidosis: new strategies for treatment

Amyloidosis is a disorder of protein folding in which normally soluble proteins are deposited extracellularly as insoluble fibrils, impairing tissue structure and function. Over 20 unrelated proteins form amyloid fibrils in vivo, with fibrils sharing a lamellar cross-β sheet structure, composed of non-covalently associated protein or peptide subunits. Amyloidosis may be acquired or hereditary and local or systemic, and is defined according to the precursor protein. Of note, local amyloid deposition occurs in Alzheimer’s disease (AD) and maturity onset diabetes but their precise role in the pathogenesis of these diseases remains uncertain. Glycosaminoglycans (GAG) and the pentraxin protein, serum amyloid P (SAP) component, are universal non-fibrillar constituents of amyloid deposits that contribute to fibrillogenesis. We review potential therapies for amyloidosis, which include measures to reduce the production of amyloidogenic precursor proteins, interference with fibrillogenesis, and enhancement of amyloid clearance, either by active or passive immunisation or by destabilising deposits through removal of serum amyloid P component.     

Stabilizing proteins to prevent conformational changes required for amyloid fibril formation

Amyloid fibrillation is associated with several human maladies, such as Alzheimer’s, Parkinson’s, Huntington’s diseases, prions, amyotrophic lateral sclerosis, and type 2 diabetes diseases. Gaining insights into the mechanism of amyloid fibril formation and exploring novel approaches to fibrillation inhibition are crucial for preventing amyloid diseases. Here, we hypothesized that ligands capable of stabilizing the native state of query proteins might prevent protein unfolding, which, in turn, may reduce the propensity of proteins to form amyloid fibrils. We demonstrated the efficient inhibition of amyloid formation of the human serum albumin (HSA) (up to 85%) and human insulin (up to 80%) by a nonsteroidal anti-inflammatory drug, ibuprofen (IBFN). IBFN significantly increases the conformational stability of both HSA and insulin, as confirmed by differential scanning calorimetry (DSC). Moreover, increasing concentration of IBFN boosts its amyloid inhibitory propensity in a linear fashion by influencing the nucleation phase as assayed by thioflavin T fluorescence, transmission electron microscopy, and dynamic light scattering. Furthermore, circular dichroism analysis supported the DSC results, showing that IBFN binds to the native state of proteins and almost completely prevents their tendency to lose secondary and tertiary structures. Cell toxicity assay confirms that species formed in the presence of IBFN are less toxic to neuronal cells (SH-SY5Y). These results demonstrate the feasibility of using a small molecule to stabilize the native state of proteins, thereby preventing the amyloidogenic conformational changes, which appear to be the common link in several human amyloid diseases.     

Elongated oligomers assemble into mammalian PrP amyloid fibrils

In prion diseases, the mammalian prion protein PrP is converted from a monomeric, mainly alpha-helical state into beta-rich amyloid fibrils. To examine the structure of the misfolded state, amyloid fibrils were grown from a beta form of recombinant mouse PrP (residues 91-231). The beta-PrP precursors assembled slowly into amyloid fibrils with an overall helical twist. The fibrils exhibit immunological reactivity similar to that of ex vivo PrP Sc. Using electron microscopy and image processing, we obtained three-dimensional density maps of two forms of PrP fibrils with slightly different twists. They reveal two intertwined protofilaments with a subunit repeat of approximately 60 A. The repeating unit along each protofilament can be accounted for by elongated oligomers of PrP, suggesting a hierarchical assembly mechanism for the fibrils. The structure reveals flexible crossbridges between the two protofilaments, and subunit contacts along the protofilaments that are likely to reflect specific features of the PrP sequence, in addition to the generic, cross-beta amyloid fold.     

Early kinetics of amyloid fibril formation reveals conformational reorganisation of initial aggregates

Understanding the initial steps of protein aggregation leading to the formation of amyloid fibrils remains a challenge. Here, the kinetics of such a process is determined for a misfolding protein model, ADA2h. The double nature of the very early kinetics suggests a step model of aggregation, where the denatured polypeptide folds into an aggregated beta-intermediate that subsequently reorganises into a more organised beta-sheet-richer structure that finally results in amyloid fibre formation. To determine the regions of the protein involved in amyloidosis, we have analysed a series of mutants previously made to study ADA2h folding. Using the algorithm TANGO, we have designed mutants that should enhance or decrease aggregation. Experimental analysis of the mutants shows that the C terminus of the molecule (comprising the last and edge beta-strand) is the major contributor to amyloid fibril formation, in good agreement with theoretical predictions. Comparison with proteins with similar topology reveals that family folds do not necessarily share the same principles of protein folding and/or aggregation.     

Insights into the origin of the tendency of the PI3-SH3 domain to form amyloid fibrils

The SH3 domain of the p85alpha subunit of phosphatidylinositol 3 kinase has been found to form amyloid fibrils in vitro under acidic conditions. PI3-SH3 is peculiar due to a large insertion of 15 amino acid residues in the n-Src loop when compared with more canonical members of the family. Spectrin-SH3 (SPC-SH3) with a shorter loop does not form fibrils under any of our conditions tested. Thus, it could be that the longer loop could play a role in amyloid formation. To investigate this we have engineered two chimeras containing the common core of the PI3-SH3 and SPC-SH3 with an exchanged n-Src loop. Thermodynamic and kinetic analyses show that the two chimeras are less stable than the parent proteins, but useful for our comparative purposes they have similar stability. Neither stability, nor folding rates, or pH transition can be invoked as being responsible for the amyloid formation in the PI3-SH3 domain. Substitution of the long n-Src loop in PI3-SH3 by that of SPC-SH3 does not prevent fibril formation. The SPC-SH3 with the PI3-SH3 n-Src loop is in an A-state at low pH and forms beta-sheet amorphous aggregates, but not amyloid fibrils. Thus, we conclude that, for a protein to form ordered fibrils, a delicate balance between solubility of non-native states to allow efficient nucleation and the formation of amorphous aggregates, must be achieved. It is the amino acid residue sequence of the protein and probably its parts that play a determinant role in shifting this balance in one direction or the other.     

Protein aggregation and amyloid fibril formation by an SH3 domain probed by limited proteolysis

The SH3 domains are small protein modules of 60-85 amino acid residues that are found in many proteins involved in intracellular signal transduction. The SH3 domain of the p85alpha subunit of bovine phosphatidylinositol 3'-kinase (PI3-SH3) under acidic solution adopts a compact denatured state from which amyloid fibrils are readily formed. This aggregation process has been found to be modulated substantially by solution conditions. Here, we have analyzed the conformational features of the native and acid denatured states of PI3-SH3 by limited proteolysis experiments using proteinase K and pepsin, respectively. Moreover, we have analyzed the propensity of PI3-SH3 to be hydrolyzed by pepsin at different stages in the process of aggregation and amyloid formation at pH 1.2 and 2.0 and compared the sites of proteolysis under these conditions with the conformational features of both native and aggregated PI3-SH3. The results demonstrate that the denatured state of PI3-SH3 formed at low pH is relatively resistant to proteolysis, indicating that it is partially folded. The long loop connecting beta-strands b and c in the native protein is the region in this structure most susceptible to proteolysis. Remarkably, aggregates of PI3-SH3 that are formed initially from this denatured state in acid solution display enhanced susceptibility to proteolysis of the long loop, suggesting that the protein becomes more unfolded in the early stages of aggregation. By contrast, the more defined amyloid fibrils that are formed over longer periods of time are completely resistant to proteolysis. We suggest that the protein aggregates formed initially are relatively dynamic species that are able readily to reorganize their interactions to enable formation of very well ordered fibrillar structures. In addition, the disordered and non-native character of the polypeptide chains in the early aggregates could be important in determining the high cytotoxicity that has been revealed in previous studies of these species.     

Cooperative hydrogen bonding in amyloid formation

Amyloid diseases, including Alzheimer's and prion diseases, are each associated with unbranched protein fibrils. Each fibril is made of a particular protein, yet they share common properties. One such property is nucleation-dependent fibril growth. Monomers of amyloid-forming proteins can remain in dissolved form for long periods, before rapidly assembly into fibrils. The lag before growth has been attributed to slow kinetics of formation of a nucleus, on which other molecules can deposit to form the fibril. We have explored the energetics of fibril formation, based on the known molecular structure of a fibril-forming peptide from the yeast prion, Sup35, using both classical and quantum (density functional theory) methods. We find that the energetics of fibril formation for the first three layers are cooperative using both methods. This cooperativity is consistent with the observation that formation of amyloid fibrils involves slow nucleation and faster growth.     

Dissociation from the oligomeric state is the rate-limiting step in fibril formation by kappa-casein

Amyloid fibrils are aggregated and precipitated forms of protein in which the protein exists in highly ordered, long, unbranching threadlike formations that are stable and resistant to degradation by proteases. Fibril formation is an ordered process that typically involves the unfolding of a protein to partially folded states that subsequently interact and aggregate through a nucleation-dependent mechanism. Here we report on studies investigating the molecular basis of the inherent propensity of the milk protein, kappa-casein, to form amyloid fibrils. Using reduced and carboxymethylated kappa-casein (RCMkappa-CN), we show that fibril formation is accompanied by a characteristic increase in thioflavin T fluorescence intensity, solution turbidity, and beta-sheet content of the protein. However, the lag phase of RCMkappa-CN fibril formation is independent of protein concentration, and the rate of fibril formation does not increase upon the addition of seeds (preformed fibrils). Therefore, its mechanism of fibril formation differs from the archetypal nucleation-dependent aggregation mechanism. By digestion with trypsin or proteinase K and identification by mass spectrometry, we have determined that the region from Tyr(25) to Lys(86) is incorporated into the core of the fibrils. We suggest that this region, which is predicted to be aggregation-prone, accounts for the amyloidogenic nature of kappa-casein. Based on these data, we propose that fibril formation by RCMkappa-CN occurs through a novel mechanism whereby the rate-limiting step is the dissociation of an amyloidogenic precursor from an oligomeric state rather than the formation of stable nuclei, as has been described for most other fibril-forming systems.     

Does the location of a mutation determine the ability to form amyloid fibrils?

We have previously reported studies of fibril formation by a set of protein G B1 domain (beta1) variants, with mutations located around the central parallel beta-strands. In this study, we designed multiple mutations in the edge strands of beta1 to create proteins with a stability range comparable to that of the set of central mutants. All the edge variants are able to form amyloid fibrils when they are incubated at their melting temperatures. This result suggests that overall protein stability is the key determinant for amyloid formation and not the specific location of destabilizing mutations. The edge strand and variants cross-seed with each other and with members of the central variant family. Interesting fibrillar morphology was observed in some cross-seeding cases and its implications for a better understanding of nucleation and elongation events are discussed.     

Large proteins have a great tendency to aggregate but a low propensity to form amyloid fibrils

The assembly of soluble proteins into ordered fibrillar aggregates with cross-β structure is an essential event of many human diseases. The polypeptides undergoing aggregation are generally small in size. To explore if the small size is a primary determinant for the formation of amyloids under pathological conditions we have created two databases of proteins, forming amyloid-related and non-amyloid deposits in human diseases, respectively. The size distributions of the two protein populations are well separated, with the systems forming non-amyloid deposits appearing significantly larger. We have then investigated the propensity of the 486-residue hexokinase-B from Saccharomyces cerevisiae (YHKB) to form amyloid-like fibrils in vitro. This size is intermediate between the size distributions of amyloid and non-amyloid forming proteins. Aggregation was induced under conditions known to be most effective for amyloid formation by normally globular proteins: (i) low pH with salts, (ii) pH 5.5 with trifluoroethanol. In both situations YHKB aggregated very rapidly into species with significant β-sheet structure, as detected using circular dichroism and X-ray diffraction, but a weak Thioflavin T and Congo red binding. Moreover, atomic force microscopy indicated a morphology distinct from typical amyloid fibrils. Both types of aggregates were cytotoxic to human neuroblastoma cells, as indicated by the MTT assay. This analysis indicates that large proteins have a high tendency to form toxic aggregates, but low propensity to form regular amyloid in vivo and that such a behavior is intrinsically determined by the size of the protein, as suggested by the in vitro analysis of our sample protein.     

与人类疾病相关的淀粉样短肽

有些天然蛋白质可通过错误折叠形成淀粉样纤维,并进一步沉积导致淀粉样病变,被认为是许多重大人类疾病的病理基础。因此,阐明天然蛋白质错误折叠、聚集形成淀粉样纤维的分子机制,是预防、诊断和治疗相关疾病的关键。研究者们从天然蛋白质中鉴定出许多能够形成淀粉样纤维的关键短肽片段,即淀粉样短肽,对它们形成淀粉样纤维的能力及其在完整蛋白质聚集过程中的决定性作用进行深入研究。本文对近年来人类疾病相关淀粉样短肽的研究展开综述。首先,介绍鉴定淀粉样短肽的标准及其相应的研究方法和技术手段;并回顾近年来与一些重大人类疾病相关的淀粉样短肽,尤其是与神经退行性疾病相关淀粉样短肽的进展情况,对淀粉样短肽中出现频率较高的氨基酸残基及其可能的自组装原理进行总结分析;最后,展望这些淀粉样短肽作为靶点在相关疾病诊断和治疗方面的意义,并初步探讨它们作为新型生物材料在生物医学工程领域的应用前景。本文一方面为阐明天然蛋白质形成淀粉样沉淀的分子机制提供参考,另一方面也为相关疾病的治疗提供思路,同时也为新型生物材料的开发提出潜在的可能性。