zhuo chen - Academia.edu (original) (raw)
Papers by zhuo chen
European Journal of Biochemistry, 1991
Drosophila alcohol dehydrogenase (ADH), an NAD(+)-dependent dehydrogenase, shares little sequence... more Drosophila alcohol dehydrogenase (ADH), an NAD(+)-dependent dehydrogenase, shares little sequence similarity with horse liver ADH. However, these two enzymes do have substantial similarity in their secondary structure at the NAD(+)-binding domain [Benyajati, C., Place, A. P., Powers, D. A. & Sofer, W. (1981) Proc. Natl Acad. Sci. USA 78, 2717-2721]. Asp38, a conserved residue between Drosophila and horse liver ADH, appears to interact with the hydroxyl groups of the ribose moiety in the AMP portion of NAD+. A secondary-structure comparison between the nucleotide-binding domain of NAD(+)-dependent enzymes and that of NADP(+)-dependent enzymes also suggests that Asp38 could play an important role in cofactor specificity. Mutating Asp38 of Drosophila ADH into Asn38 decreases Km(app)NADP 62-fold and increases kcat/Km(app)NADP 590-fold at pH 9.8, when compared with wild-type ADH. These results suggest that Asp38 is in the NAD(+)-binding domain and its substituent, Asn38, allows Drosophila ADH to use both NAD+ and NADP+ as its cofactor. The observations from the experiments of thermal denaturation and kinetic measurement with pH also confirm that the repulsion between the negative charges of Asp38 and 2'-phosphate of NADP+ is the major energy barrier for NADP+ to serve as a cofactor for Drosophila ADH.
Experimental Eye Research, 2004
Stem Cells, 2004
This study evaluated proposed molecular markers related to stem cell (SC) properties with the int... more This study evaluated proposed molecular markers related to stem cell (SC) properties with the intention of characterizing a putative SC phenotype in human limbal epithelia. Human corneal and limbal tissues were cut in the vertical and horizontal meridians for histology, transmission electron microscopy (TEM), and immunostaining. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization were used to evaluate gene expression. TEM showed that the limbal basal cells were small primitive cells. Immunostaining disclosed that p63, ABCG2 and integrin α9 were primarily expressed by the basal epithelial cells of limbus. Antibodies against integrin β1, epidermal growth factor receptor (EGFR), K19, enolase-α, and CD71 stained the basal cells of the limbus more brightly than the suprabasal epithelia. Integrin α6, nestin, E-cadherin and connexin 43 did not stain the limbal basal cells, but the suprabasal epithelia of the cornea and limbus showed strong immunoreactivity. K3 and involucrin stained only corneal and limbal superficial cells. RT-PCR showed higher levels of p63, ABCG2 and integrin α9 mRNA, but lower levels of K3, K12 and connexin 43 expressed in the limbal epithelia than the corneal epithelia. In situ hybridization showed that p63 transcripts were located in basal layer of the limbal epithelium. This work suggests that the basal epithelial cells of the limbus are p63, ABCG2 and integrin α9 positive, and nestin, E-cadherin, connexin 43, involucrin, K3, and K12 negative, with relatively higher expression of integrin β1, EGFR, K19, and enolase-α. This putative SC phenotype may facilitate the identification and isolation of limbal epithelial SCs.
American Journal of Ophthalmology, 2006
Stem Cells, 2005
ABCG2, a member of the ATP binding cassette (ABC) transporters, has been identified as a molecula... more ABCG2, a member of the ATP binding cassette (ABC) transporters, has been identified as a molecular determinant for bone marrow stem cells and proposed as a universal marker for stem cells. This study investigates ABCG2 expression and its potential as a marker that identifies human limbal epithelial stem cells. ABCG2 expression was evaluated by immunofluorescent and immunohistochemical staining, laser scanning confocal microscopy, flow cytometry, and semiquantitative reverse transcription–polymerase chain reaction. Cells selected from primary limbal epithelial cultures by flow cytometry with ABCG2 monoclonal antibody (mAb) or Hoechst 33342 dye staining were evaluated for their gene expression and colony-forming efficiency (CFE). ABCG2 protein was mainly located in the basal cells of limbal epithelia but not in the limbal suprabasal and corneal epithelia. ABCG2 staining was also observed in primary limbal epithelial cultures. Limbal epithelia express higher levels of ABCG2 and ΔNp63 mRNAs than corneal epithelia. Labeling with ABCG2 mAb yielded 2.5%–3.0% positive cells by flow cytometry. The ABCG2-positive cells exhibited greater CFE on a 3T3 fibroblast feeder layer than ABCG2-negative cells. A side population (SP) was detected by the Hoechst 33342 exclusion assay. SP cells displayed stronger expression of ABCG2 and ΔNp63 mRNA and greater CFE than the non-SP cells. In conclusion, these findings demonstrate that ABCG2 transporter was exclusively expressed by limbal basal cells and that the ABCG2-positive and SP cells possess enriched stem cell properties, suggesting for the first time that ABCG2 could serve as a marker to identify the putative limbal epithelial stem cells.
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the
IEEE Transactions on Communications, 2003
Electronics Letters, 2003
In this paper, we propose an improved relay selection scheme based on a hybrid relaying protocol ... more In this paper, we propose an improved relay selection scheme based on a hybrid relaying protocol (RS-HRP). In the proposed scheme, all the relays are included into two groups, referred to as an amplify and forward (AAF) and a decode and forward (DAF) relay groups. The relays which decode successfully are included in the DAF group and the rest of
IEEE Communications Letters, 2002
Eurasip Journal on Advances in Signal Processing, 2002
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the multiple fading subchannels between individual transmit and receive antenna pairs converge to an additive white Gaussian noise (AWGN) channel and the design of codes with maximum coding gain is governed by the minimum trace of the distance matrices, or the minimum Euclidean distance between any two codewords over all transmit antennas. A number of new 4 and 8-PSK codes based on the proposed design criterion were constructed and shown to be superior to other known codes
IEEE Transactions on Wireless Communications, 2009
Abstract It has been established that the appropriate design parameters for space-time trellis co... more Abstract It has been established that the appropriate design parameters for space-time trellis code (STTC) in quasi-static flat Rayleigh fading channels are the rank and determinant criteria or the Euclidean distance criterion, depending on the value of the overall diversity ...
Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. I... more Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. It is shown that the code performance is dominated by the minimum rank r and the minimum determinant of the codeword distance matrix when the product of the minimum rank r and the number of receive antennas nR is less than 4, which is consistent with
Abstract Multiple antenna systems have the potential to provide a high capacity wireless communic... more Abstract Multiple antenna systems have the potential to provide a high capacity wireless communication system. The spectral efficiency of space time trellis coding (STTC) is limited by the encoder structure. The layered space time (LST) architecture can overcome this ...
Electronics Letters, 2001
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the
European Journal of Biochemistry, 1991
Drosophila alcohol dehydrogenase (ADH), an NAD(+)-dependent dehydrogenase, shares little sequence... more Drosophila alcohol dehydrogenase (ADH), an NAD(+)-dependent dehydrogenase, shares little sequence similarity with horse liver ADH. However, these two enzymes do have substantial similarity in their secondary structure at the NAD(+)-binding domain [Benyajati, C., Place, A. P., Powers, D. A. & Sofer, W. (1981) Proc. Natl Acad. Sci. USA 78, 2717-2721]. Asp38, a conserved residue between Drosophila and horse liver ADH, appears to interact with the hydroxyl groups of the ribose moiety in the AMP portion of NAD+. A secondary-structure comparison between the nucleotide-binding domain of NAD(+)-dependent enzymes and that of NADP(+)-dependent enzymes also suggests that Asp38 could play an important role in cofactor specificity. Mutating Asp38 of Drosophila ADH into Asn38 decreases Km(app)NADP 62-fold and increases kcat/Km(app)NADP 590-fold at pH 9.8, when compared with wild-type ADH. These results suggest that Asp38 is in the NAD(+)-binding domain and its substituent, Asn38, allows Drosophila ADH to use both NAD+ and NADP+ as its cofactor. The observations from the experiments of thermal denaturation and kinetic measurement with pH also confirm that the repulsion between the negative charges of Asp38 and 2'-phosphate of NADP+ is the major energy barrier for NADP+ to serve as a cofactor for Drosophila ADH.
Experimental Eye Research, 2004
Stem Cells, 2004
This study evaluated proposed molecular markers related to stem cell (SC) properties with the int... more This study evaluated proposed molecular markers related to stem cell (SC) properties with the intention of characterizing a putative SC phenotype in human limbal epithelia. Human corneal and limbal tissues were cut in the vertical and horizontal meridians for histology, transmission electron microscopy (TEM), and immunostaining. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization were used to evaluate gene expression. TEM showed that the limbal basal cells were small primitive cells. Immunostaining disclosed that p63, ABCG2 and integrin α9 were primarily expressed by the basal epithelial cells of limbus. Antibodies against integrin β1, epidermal growth factor receptor (EGFR), K19, enolase-α, and CD71 stained the basal cells of the limbus more brightly than the suprabasal epithelia. Integrin α6, nestin, E-cadherin and connexin 43 did not stain the limbal basal cells, but the suprabasal epithelia of the cornea and limbus showed strong immunoreactivity. K3 and involucrin stained only corneal and limbal superficial cells. RT-PCR showed higher levels of p63, ABCG2 and integrin α9 mRNA, but lower levels of K3, K12 and connexin 43 expressed in the limbal epithelia than the corneal epithelia. In situ hybridization showed that p63 transcripts were located in basal layer of the limbal epithelium. This work suggests that the basal epithelial cells of the limbus are p63, ABCG2 and integrin α9 positive, and nestin, E-cadherin, connexin 43, involucrin, K3, and K12 negative, with relatively higher expression of integrin β1, EGFR, K19, and enolase-α. This putative SC phenotype may facilitate the identification and isolation of limbal epithelial SCs.
American Journal of Ophthalmology, 2006
Stem Cells, 2005
ABCG2, a member of the ATP binding cassette (ABC) transporters, has been identified as a molecula... more ABCG2, a member of the ATP binding cassette (ABC) transporters, has been identified as a molecular determinant for bone marrow stem cells and proposed as a universal marker for stem cells. This study investigates ABCG2 expression and its potential as a marker that identifies human limbal epithelial stem cells. ABCG2 expression was evaluated by immunofluorescent and immunohistochemical staining, laser scanning confocal microscopy, flow cytometry, and semiquantitative reverse transcription–polymerase chain reaction. Cells selected from primary limbal epithelial cultures by flow cytometry with ABCG2 monoclonal antibody (mAb) or Hoechst 33342 dye staining were evaluated for their gene expression and colony-forming efficiency (CFE). ABCG2 protein was mainly located in the basal cells of limbal epithelia but not in the limbal suprabasal and corneal epithelia. ABCG2 staining was also observed in primary limbal epithelial cultures. Limbal epithelia express higher levels of ABCG2 and ΔNp63 mRNAs than corneal epithelia. Labeling with ABCG2 mAb yielded 2.5%–3.0% positive cells by flow cytometry. The ABCG2-positive cells exhibited greater CFE on a 3T3 fibroblast feeder layer than ABCG2-negative cells. A side population (SP) was detected by the Hoechst 33342 exclusion assay. SP cells displayed stronger expression of ABCG2 and ΔNp63 mRNA and greater CFE than the non-SP cells. In conclusion, these findings demonstrate that ABCG2 transporter was exclusively expressed by limbal basal cells and that the ABCG2-positive and SP cells possess enriched stem cell properties, suggesting for the first time that ABCG2 could serve as a marker to identify the putative limbal epithelial stem cells.
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the
IEEE Transactions on Communications, 2003
Electronics Letters, 2003
In this paper, we propose an improved relay selection scheme based on a hybrid relaying protocol ... more In this paper, we propose an improved relay selection scheme based on a hybrid relaying protocol (RS-HRP). In the proposed scheme, all the relays are included into two groups, referred to as an amplify and forward (AAF) and a decode and forward (DAF) relay groups. The relays which decode successfully are included in the DAF group and the rest of
IEEE Communications Letters, 2002
Eurasip Journal on Advances in Signal Processing, 2002
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the multiple fading subchannels between individual transmit and receive antenna pairs converge to an additive white Gaussian noise (AWGN) channel and the design of codes with maximum coding gain is governed by the minimum trace of the distance matrices, or the minimum Euclidean distance between any two codewords over all transmit antennas. A number of new 4 and 8-PSK codes based on the proposed design criterion were constructed and shown to be superior to other known codes
IEEE Transactions on Wireless Communications, 2009
Abstract It has been established that the appropriate design parameters for space-time trellis co... more Abstract It has been established that the appropriate design parameters for space-time trellis code (STTC) in quasi-static flat Rayleigh fading channels are the rank and determinant criteria or the Euclidean distance criterion, depending on the value of the overall diversity ...
Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. I... more Novel code design criteria for space-time codes on slow Rayleigh fading channels are presented. It is shown that the code performance is dominated by the minimum rank r and the minimum determinant of the codeword distance matrix when the product of the minimum rank r and the number of receive antennas nR is less than 4, which is consistent with
Abstract Multiple antenna systems have the potential to provide a high capacity wireless communic... more Abstract Multiple antenna systems have the potential to provide a high capacity wireless communication system. The spectral efficiency of space time trellis coding (STTC) is limited by the encoder structure. The layered space time (LST) architecture can overcome this ...
Electronics Letters, 2001
It has been established that the appropriate criteria for space-time trellis coded modulation (ST... more It has been established that the appropriate criteria for space-time trellis coded modulation (STTCM) design on slow Rayleigh fading channels are maximization of the minimum rank and the minimum determinant of the distance matrices. We show here that when STTCM is used in systems with a large product of the numbers of the transmit and the receive antennas (>3), the