Background/PurposeThe VPAC1 receptor, a member of the vasoactive intestinal peptide receptors (VIPRs), is overexpressed in the most frequently occurring malignant tumors and plays a major role in the progression and angiogenesis of a number of malignancies. Recently, phage display has become widely used for many applications, including ligand generation for targeted imaging, drug delivery and therapy. In this work, we developed a panning procedure using a phage display peptide library to select a peptide that specifically binds to the VPAC1 receptor to develop a novel targeted probe for molecular imaging and therapy.MethodsCHO-K1 cells stably expressing VPAC1 receptors (CHO-K1/VPAC1 cells) were used to select a VPAC1-binding peptide from a 12-mer phage peptide library. DNA sequencing and homologous analysis of the randomly selected phage clones were performed. A cellular ELISA was used to determine the most selectively binding peptide for further investigation. Binding specificity to the VPAC1 receptor was analyzed by competitive inhibition ELISA and flow cytometry. The binding ability of the selected peptide to CHO-K1/VPAC1 cells and colorectal cancer (CRC) cell lines was confirmed using fluorescence microscopy and flow cytometry.ResultsA significant enrichment of phages that specifically bound to CHO-K1/VPAC1 cells was obtained after four rounds of panning. Of the selected phage clones, 16 out of 60 shared the same peptide sequence, GFRFGALHEYNS, which we termed the VP2 peptide. VP2 and vasoactive intestinal peptide (VIP) competitively bound to the VPAC1 receptor. More importantly, we confirmed that VP2 specifically bound to CHO-K1/VPAC1 cells and several CRC cell lines.ConclusionOur results demonstrate that the VP2 peptide could specifically bind to VPAC1 receptor and several CRC cell lines. And VP2 peptide may be a potential candidate to be developed as a useful diagnostic molecular imaging probe for early detection of CRC.
Thermally driven heat pump systems play important roles in the utilization of low-grade thermal energy. In order to evaluate and compare the performances of three different constructions of thermally driven heat pump and heat transformer, the low-dissipation assumption has been adopted to establish the irreversible thermodynamic models of them in the present paper. By means of the proposed models, the heating loads, the coefficients of performance (COPs) and the optimal relations between them for various constructions are derived and discussed. The performances of different constructions are numerically assessed. More importantly, according to the results obtained, the upper and lower bounds of the COP at maximum heating load for different constructions are generated and compared by the introduction of a parameter measuring the deviation from the reversible limit of the system. Accordingly, the optimal constructions for the low-dissipation three-terminal heat pump and heat transformer are determined within the frame of low-dissipation assumption, respectively. The optimal constructions in accord with previous research and engineering practices for various three-terminal devices are obtained, which confirms the compatibility between the low-dissipation model and endoreversible model and highlights the validity of the application of low-dissipation model for multi-terminal thermodynamic devices. The proposed models and the significant results obtained enrich the theoretical thermodynamic model of thermally driven heat pump systems and may provide some useful guidelines for the design and operation of realistic thermally driven heat pump systems.
The construction of smart grid uses a large number of power electronic equipment, which leads to the increase of harmonic content of transformer core winding, and brings some difficulties to the calculation of core loss. In order to study the influence of harmonics on core loss, a dynamic hysteresis loss model of transformer core under harmonics is established. On the basis of J-A static hysteresis model, the calculation methods of eddy current loss and abnormal loss under harmonic wave are deduced, and the calculation method of core loss under harmonic wave is established according to the principle of energy conservation. The core loss of three-phase transformer is simulated and verified by experiments under different harmonic frequency and harmonic voltage percentage. The results verify the validity of the model.
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