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BACKGROUND: Traditionally,UV/visible spectra,conductivity,electrophoresis and other methods are commonly applied for studying the interaction of metal ions and amino acids,but UV-Vis spectroscopy and fluorescence spectroscopy for L-histidine reacted with silver ion in aqueous solution is rarely reported.OBJECTIVE: To investigate the interaction between silver ion and histidine using UVNIS and fluorescence spectra.METHODS: The influence of pH,multicomponent concentration such as histidine,silver ion,formaldehyde,sodium dodecyl sulfate and trihydroxymethyl aminomethane,as well as illumination strength and time,on the interaction between silver ion and histidine were investigated,and the mechanism of reaction was also explored.RESULTS AND CONCLUSION: Applied pH potentiometer titration method,the dissociation constants of histidine was defined 9.21.The stepwise stability constants of histidine-silver was logK1=5.56 and logK2=4.05,respectively by using half(n)method.At 20 ℃,the electric potential of histidine-silver system was 2.10×10-4 V.According to pH potentiometer titration and lob method,the compound was consisted of histidine: Ag=2:1.Compared with histidine,histidine-silver systems reached a shoulder peak at 295.3 nm,which was assigned to conjugate double bond of imidazole ring that easily generated π-π*transition.And an absorption peak close to 242 nm can be assigned to n-π*transition of the C=O group of the histidine-silver.The fluorescence emission spectra of histidine-silver systems belonged to 5D0→7F2 electric dipole transition.Compared with reference solutions under the same conditions,it not only emitted wavelengths blue shift,but also induced fluorescence quenching.Results showed that,imidazole ring was involved in the bonding action with silver ion.The reaction process is to firstly generate six-coordination complex,secondly reduce the silver ion into ultrafine silver particles which are bound by histidine.
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Objective To evaluate the MRI findings and its diagnostic value in gluteal muscle contracture (GMC). Methods Eleven clinic or operation confirmed GMC patients were examined by plain X-ray and MRI. Conventional T 1WI and T 2WI MR imaging were performed and FFE-T 2WI (fast field echo-T 2WI) was also scanned. CT scan was conducted in 5 cases. Results 11 GMC patients were all diagnosed by MRI. Conventional T 1WI and T 2WI could only show the atrophy of gluteal muscles, while FFE-T 2WI could directly show the fibrous band of gluteal muscle and its fascia, and the fibrous band appeared as low signal intensity on FFE-T 2WI sequence. Conclusions MRI is the efficient modality in imaging the fibrous band for GMC patients, and FFE-T 2WI is the most valuable sequence. MRI is very helpful in the diagnosis and treatment of GMC.
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Objective To evaluate the appearances of osteochondral fracture of the knee on X-ray and MR imaging. Methods Twelve patients with knee acute injury were examined with X-ray and MRI. The findings of MRI and X-ray were analyzed and reviewed, and the results of each patient were confirmed by arthroscopy and operation. Results Thirteen areas of osteochondral fracture including 9 loose bodies in 12 patients were diagnosed by MRI. Seven locations were found by MRI in the distal lateral femoral condyle, and 6 in patellar. MRI could clearly show the location, the size, and the depth of each osteochondral fracture, and MRI could also differentiate the articular cartilage and the subchondral of the loose body. T 2WI, STIR, and FFE-T 2WI were the best sequences to demonstrate the osteochondral fracture. X-ray showed 5 loose bodies in the knee joint, but could not detect where they came from. Conclusion MRI can accurately reveal and diagnose the osteochondral fracture of knee after trauma, which improves the diagnostic certainty and is very helpful for arthroscopy and operation. X-ray is still the initial modality in detecting the osteochondral fracture of knee and should be combined with MRI to confirm the diagnosis.
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Objective To evaluate the value of MRI in diagnosing pigmented villonodular synovitis (PVNS). Methods MRI appearance of 23 pathologically proven cases of PVNS was analyzed. Results In 23 patients with PVNS, 9 cases occurred in knee joint, 9 cases in hip, 3 cases in ankle, 1 in elbow, and 1 in wrist. X ray of the 23 patients could only show the joint effusion, and bony erosion was found in 19 cases. CT scan showed joint effusion and bony erosion more clearly than X ray in 4 cases. The typical MRI appearance included intra articular joint effusion and extensive synovial proliferation which led to progressive destruction of cartilage and bone. The pigmented villonodules showed nodular low signal on both T 1WI and T 2WI, especially in FFE/T 2WI. Conclusion MRI is the most effective modality in the diagnosis of PVNS.