Lirong He,Sumei Cai,Bo Wu,Changdao Mu,Guangzhao Zhang,Wei Lin
Ultrasensitive differential scanning calorimetry (US-DSC) was used to directly measure the thermal transition temperature and energy change of acid soluble collagen in the presence of Cr 3 + and Al 3 + sulfates. The behavior of Cr 3 + was analogous to kosmotropes in the cation Hofmeister series and increased the stability of collagen in dilute solutions. Meanwhile, the denaturational enthalpy change (Δ H ) of collagen was substantially reduced with change to increasing Cr 3 + concentration. This is likely due to the uni-point binding of Cr 3 + with carboxyl groups of collagen side chains that could decrease the hydrogen-bonding in collagen and result in the increase of protein hydrophobicity . In the case of Al 3 + , the interactions between the ions and collagen showed very different properties: at low and medium ion concentrations, the stability of the collagen was decreased; however, a further increase of Al 3 + concentration led to a salting-out effect of collagen, indicating the Al 3 + is a typical chaotropic ion. This striking difference of the two ions in the stabilization of collagen can be explained in terms of the different interactions between the cations and the carboxyl groups of collagen side chains. Additionally, we studied metal ion induced conformational change by the combination of circular dichroism (CD) and atomic force microscopy (AFM). CD measurements revealed that neither metal ion interactions of collagen with Cr 3 + nor Al 3 + ions destroyed the triple-helical backbone structure of collagen in the solution. AFM results further confirmed that the dehydration of collagen by Cr 3 + is more significant than Al 3 + , thus inducing the aggregation of collagen fibrils.
7,7,8,8-tetracyanoquinodimethane (TCNQ) is a low-cost redox active organic compound which has high theoretic specific capacity. But when it is used as cathode material in batteries , it always suffers from fast performance decaying because of material dissolution. In this work, Al 3+ salt is added in a Na 2 SO 4 /ZnSO 4 aqueous electrolyte to stabilize the crystalline structure of TCNQ and depress its solubility. Surprisingly, we found the insertion/extraction of high valent cations (Al 3+ and Zn 2+ ) in TCNQ is highly reversible, which leads to synergistic improvement of both specific capacity and cycle life. The obtained cathode exhibits a reversible capacity of 245.8 mAh g -1 at 0.5 A g -1 and a cycle-life of 1000 rounds at 3 A g -1 . Our work demonstrates that molecular organic electrode materials are very different from conventional inorganic cathode materials in terms of high valent cation intercalation reversibility. Adding high valent cation salts is a simple and effective way to enhance the electrochemical performance of molecular organic electrode materials, and consequently build low cost, high performance aqueous rechargeable batteries.
The formation and accumulation of toxic amyloid beta (Aβ) protofibrils in brain is recognized as the pathological hallmark of alzheimer’s disease (AD). Recent research indicated that photodynamic therapy (PDT) has potential to treat AD because reactive oxygen species (ROS) generated by photosensitizers (PS) could degrades Aβ protofibrils. Al 3+ and Fe 3+ were found at markedly high levels on and around Aβ protofibrils comparing with the normal part of brain. Based on this, a thymine modified Zn phthalocyanine (T-ZnPc), which can specific recognize and has strong affinity with Fe 3+ and Al 3+ , was designed and synthesized. The recognize, affinity, Aβ protofibrils degradation and neuro protection process were monitored via ultraviolet absorption spectrometry (UV), fluorescence emission spectrum, transmission electron microscopy (TEM), flow cytometer and thiazolyl blue tetrazolium bromide (MTT) assay. The results revealed that such affinity effect greatly increases the molar extinction coefficient (from 1.70 × 10 4 to 4.67 × 10 4 and 3.30 × 10 4 after forming Fe-T-ZnPc and Al-T-ZnPc) and activates PDT activity of T-ZnPc to generate abundant ROS to degrade Aβ protofibrils (62% and 81% degradation by Al-T-ZnPc and Fe-T-ZnPc) and prevent its neurotoxicity based on the statistical differences analysis. Besides, T-ZnPc could inhibit new Aβ protofibrils formation and the chelation effect could reduce the free Fe 3+ and Al 3+ concentration in brain, which could be also helpful for AD treatment.
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