Suniya Shahzad | Quaid-i-Azam University, Islamabad, Pakistan (original) (raw)

Papers by Suniya Shahzad

Chemical Society Reviews, 2009

Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur ... more Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur either in single-step superexchange or in multistep hopping processes. Whereas the rate of the single-step electron transfer dramatically decreases with the distance, a hopping process is less distance dependent. Electron hopping is possible if amino acids carry oxidizable side chains, like the phenol group in tyrosine. These side chains become intermediate charge carriers. Because of the weak distance dependency of hopping processes, fast electron transfer over very long distances occurs in multistep reactions, as in the enzyme ribonucleotide reductase.

ChemInform, 2015

In this review, we discuss the factors that influence electron transfer in peptides. We summarize... more In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donoracceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors such as the extent of the secondary structure, backbone conformation, dipole orientation, the presence of special amino acids, hydrogen bonding, and the dynamic properties of a peptide also influence the rate and mode of electron transfer in peptides. Electron transfer plays a key role in physical, chemical and biological systems, so its control is a fundamental task in bioelectrochemical systems, the design of peptide based sensors and molecular junctions. Therefore, this topic is at the heart of a number of biological and technological processes and thus remains of vital interest.

RSC Advances, 2014

This work presents the synthesis, redox behavior and spectroscopic characterization of two novel ... more This work presents the synthesis, redox behavior and spectroscopic characterization of two novel compounds Sodium 4-(3methoxyphenyl) piperazine-1-carbodithioate and sodium 4-(4-nitrophenyl) piperazine-1-carbodithioate. Pulse voltammetric techniques were utilized to determine the number of electrons involved in the oxidation and/or the reduction step and to ensure the nature of the redox processes. The pH dependent redox mechanistic pathways of the compounds were proposed on the basis of electrochemical and computational results. Different thermodynamic parameters like G # and H # revealed that electrode processes are non-spontaneous and endergonic in nature. Increase in S # values at higher temperature indicated the randomness of the electrode reactions at higher temperatures. Limits of detection and quantification were determined by square wave voltammetry due to its high sensitivity and fast speed. Ionization energy, electron affinity, dipole moment and charge distribution on atoms were computationally determined. Acid-base dissociation constant (pKa) values of the compounds evaluated by voltammetry and electronic spectroscopy were found comparable.

Chemical Society reviews, Jan 10, 2015

In this review, we discuss the factors that influence electron transfer in peptides. We summarize... more In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donor-acceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors ...

Chemical Society Reviews, 2009

Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur ... more Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur either in single-step superexchange or in multistep hopping processes. Whereas the rate of the single-step electron transfer dramatically decreases with the distance, a hopping process is less distance dependent. Electron hopping is possible if amino acids carry oxidizable side chains, like the phenol group in tyrosine. These side chains become intermediate charge carriers. Because of the weak distance dependency of hopping processes, fast electron transfer over very long distances occurs in multistep reactions, as in the enzyme ribonucleotide reductase.

ChemInform, 2015

In this review, we discuss the factors that influence electron transfer in peptides. We summarize... more In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donoracceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors such as the extent of the secondary structure, backbone conformation, dipole orientation, the presence of special amino acids, hydrogen bonding, and the dynamic properties of a peptide also influence the rate and mode of electron transfer in peptides. Electron transfer plays a key role in physical, chemical and biological systems, so its control is a fundamental task in bioelectrochemical systems, the design of peptide based sensors and molecular junctions. Therefore, this topic is at the heart of a number of biological and technological processes and thus remains of vital interest.

RSC Advances, 2014

This work presents the synthesis, redox behavior and spectroscopic characterization of two novel ... more This work presents the synthesis, redox behavior and spectroscopic characterization of two novel compounds Sodium 4-(3methoxyphenyl) piperazine-1-carbodithioate and sodium 4-(4-nitrophenyl) piperazine-1-carbodithioate. Pulse voltammetric techniques were utilized to determine the number of electrons involved in the oxidation and/or the reduction step and to ensure the nature of the redox processes. The pH dependent redox mechanistic pathways of the compounds were proposed on the basis of electrochemical and computational results. Different thermodynamic parameters like G # and H # revealed that electrode processes are non-spontaneous and endergonic in nature. Increase in S # values at higher temperature indicated the randomness of the electrode reactions at higher temperatures. Limits of detection and quantification were determined by square wave voltammetry due to its high sensitivity and fast speed. Ionization energy, electron affinity, dipole moment and charge distribution on atoms were computationally determined. Acid-base dissociation constant (pKa) values of the compounds evaluated by voltammetry and electronic spectroscopy were found comparable.

Chemical Society reviews, Jan 10, 2015

In this review, we discuss the factors that influence electron transfer in peptides. We summarize... more In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donor-acceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors ...