Two new sickle cell syndromes: HbS, Hb Camden, and alpha-thalassemia; and HbS in combination with Hb Tacoma

Hemoglobin variants having electrophoretic mobility more rapid than that of HbA were identified in combination with sickle hemoglobin in two patients at the Cook County Hospital. Neither individual had symptomatic hematologic disease. In one patient, the rapidly migrating hemoglobin had the amino acid substitution characteristic of Hb Tacoma (beta-40 arg leads to ser), a mildly unstable variant. In the other patient, Hb Camden (beta-131 gln leads to glu) was identified, and the hematologic findings also indicated that he has alpha-thalassemia trait. In the patient with HbS-Camden--alpha-thalassemia, globin synthesis was unbalanced (alpha/beta 0.66), and HbS represented only 19.5% of the total hemoglobin. The latter finding suggests that under conditions of limited alpha-chain availability beta Camden may combine with alpha subunits at least as efficiently as does betaA. HbS represented 56% of the hemoglobin of the patient with HbS Tacoma, although the rate of synthesis of beta Tacoma by her reticulocytes was consistently greater than that of betaS. A time-course synthesis study demonstrated a progressive increase in the specific activity of beta Tacoma in relation to that of betaS, suggesting that the unstable beta- chains of Hb Tacoma underwent selective intracellular degradation. This process appears to explain the disparity between the rates of synthesis of the two beta chains and the relative representation of HbS and Hb Tacoma in the patient's erythrocytes.     

Nanoprobing of the Effect of Cu2+ Cations on Misfolding, Interaction and Aggregation of Amyloid β Peptide

Misfolding and aggregation of the amyloid β-protein (Aβ) are hallmarks of Alzheimer’s disease. Both processes are dependent on the environmental conditions, including the presence of divalent cations, such as Cu²⁺. Cu²⁺ cations regulate early stages of Aβ aggregation, but the molecular mechanism of Cu²⁺ regulation is unknown. In this study we applied single molecule AFM force spectroscopy to elucidate the role of Cu²⁺ cations on interpeptide interactions. By immobilizing one of two interacting Aβ42 molecules on a mica surface and tethering the counterpart molecule onto the tip, we were able to probe the interpeptide interactions in the presence and absence of Cu²⁺ cations at pH 7.4, 6.8, 6.0, 5.0, and 4.0. The results show that the presence of Cu²⁺ cations change the pattern of Aβ interactions for pH values between pH 7.4 and pH 5.0. Under these conditions, Cu²⁺ cations induce Aβ42 peptide structural changes resulting in N-termini interactions within the dimers. Cu²⁺ cations also stabilize the dimers. No effects of Cu²⁺ cations on Aβ-Aβ interactions were observed at pH 4.0, suggesting that peptide protonation changes the peptide-cation interaction. The effect of Cu²⁺ cations on later stages of Aβ aggregation was studied by AFM topographic images. The results demonstrate that substoichiometric Cu²⁺ cations accelerate the formation of fibrils at pH 7.4 and 5.0, whereas no effect of Cu²⁺ cations was observed at pH 4.0. Taken together, the combined AFM force spectroscopy and imaging analyses demonstrate that Cu²⁺ cations promote both the initial and the elongation stages of Aβ aggregation, but protein protonation diminishes the effect of Cu²⁺.     

Single-molecule selection and recovery of structure-specific antibodies using atomic force microscopy

Protein misfolding and aggregation are a common thread in numerous diseases including Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, diabetes, and prion-related diseases. Elucidation of the role played by the various protein forms in these diseases requires reagents that can target specific protein forms. Here we present a method to isolate antibodies that bind to a specific protein form. We combined the imaging and nanomanipulation capabilities of atomic force microscopy (AFM) with the protein diversity of phage display antibody libraries to develop a technology that allows us to recover a single antibody molecule that is bound to a single protein molecular target. The target protein-antibody complex is first imaged by AFM, the AFM tip is then manipulated by nanolithography over the target antibody to recover the associated phage, and the antibody gene is recovered from the single phage particle by polymerase chain reaction.     

New technology and clinical applications of nanomedicine: highlights of the second annual meeting of the American Academy of Nanomedicine (Part I)

The Second Annual Meeting of the American Academy of Nanomedicine (AANM) was held at the National Academy of Science Building in Washington, DC, September 9-10, 2006. The program included two Nobel Prize Laureate Lectures, two Keynote Lectures, and 123 invited outstanding State-in-Art lectures presenting in 23 special concurrent symposia. In addition, there were 22 poster presentations in the meeting addressing different areas in nanomedicine research. All of the presenters at the meeting are outstanding investigators and researchers in the field. The Second Annual Meeting of the AANM was a great success. The meeting provides investigators from different world areas a forum and an opportunity for discussion. We believe that nanomedicine research will develop rapidly in the future. The AANM invites basic and clinical researchers from the world to join this exciting research.     

Physicochemical characteristics of soluble oligomeric Abeta and their pathologic role in Alzheimer's disease

Extracellular fibrillar amyloid deposits are prominent and universal Alzheimer's disease (AD) features, but senile plaque abundance does not always correlate directly with the degree of dementia exhibited by AD patients. The mechanism(s) and dynamics of Abeta fibril genesis and deposition remain obscure. Enhanced Abeta synthesis rates coupled with decreased degradative enzyme production and accumulating physical modifications that dampen proteolysis may all enhance amyloid deposit formation. Amyloid accumulation may indirectly exert the greatest pathologic effect on the brain vasculature by destroying smooth muscle cells and creating a cascade of negative impacts on cerebral blood flow. The most visible manifestation of amyloid dis-equilibrium could actually be a defense mechanism employed to avoid serious vascular wall degradation while the major toxic effects to the gray and white matter neurons are mediated by soluble oligomeric Abeta peptides with high beta-sheet content. The recognition that dynamic soluble oligomeric Abeta pools exist in AD and are correlated to disease severity led to neurotoxicity and physical conformation studies. It is now recognized that the most basic soluble Abeta peptides are stable dimers with hydrophobic regions sequestered from the aqueous environment and are capable of higher order aggregations. Time course experiments employing a modified ELISA method able to detect Abeta oligomers revealed dynamic intermolecular interactions and additional experiments physically confirmed the presence of stable amyloid multimers. Amyloid peptides that are rich in beta-sheet structure are capable of creating toxic membrane ion channels and a capacity to self-assemble as annular structures was confirmed in vitro using atomic force microscopy. Biochemical studies have established that soluble Abeta peptides perturb metabolic processes, provoke release of deleterious reactive compounds, reduce blood flow, induce mitochondrial apoptotic toxicity and inhibit angiogenesis. While there is no question that gross amyloid deposition does contribute to AD pathology, the destructive potential now associated with soluble Abeta suggests that treatment strategies that target these molecules may be efficacious in preventing some of the devastating effects of AD.     

迷迭香酸抗血栓和抗血小板聚集作用

迷迭香酸是丹参水溶性成分之一。大鼠体内实验(iv)表明,它能抑制静脉血栓形成。阻抑胶原诱导的血小板聚集,促进纤维蛋白溶解活性。当剂量为50及100 mg/kg时,血栓形成的抑制率分别为41.9和54.8%(P<0.vv05)。当剂量为100及150mg/kg时,血小板聚集的抑制率分别为30.4%(P<0.05)和46.4%(P<0.01),血浆优球蛋白溶解时间缩短(P<0.05)。纤维蛋白原含量无明显变化。以上结果说明,迷迭香酸有温和的抗血栓作用。其机理可能与抗血小板聚集和增强纤维蛋白溶解活性有关。