Three single-position Peltier thermostatted cell holders are available with a maximum light path length of 10 mm, to enable temperature control using the temperature control program. All feature a temperature setting range of -30 to 130°C with a measurement probe that can be placed inside or adjacent to cell and a magnetic stirrer to eliminate thermal gradients.

The MPTC accessories are designed to enable high sample throughput and productivity. The six-position holder for rectangular cells allows automated spectral scans and parallel thermal ramps on up to six samples at a time. All feature a temperature setting range of -30 to 130°C with a measurement probe that can be placed inside or adjacent to cell and a magnetic stirrer to eliminate thermal gradients.

Stopped-flow measurements involve the rapid mixing of two or more solutions to trigger a chemical reaction. The reaction kinetics can then be followed by CD, absorbance and fluorescence. All measurement techniques can be acquired on the same instrument when the stopped-flow system is paired with a J-1500 or J-1700 spectrophotometer.

Optical Rotatory Dispersion (ORD) provides information on chiral molecules even without chromophores, such as saccharides. It can be used to measure the chirality of non-absorbing samples and the determination of absolute configuration.
JASCO offers two methods of ORD detection: optical null and intensity measurement systems. The intensity measurement method, using a fixed analyzer, is simpler and more economical, while the optical-null approach, with its rotating analyzer, is intrinsically more accurate because the measurement is absolute. Since ORD is very sensitive to strain in the sample cell window, cylindrical cells are strongly recommended for use ORD measurement.

In the case of samples where only very small volumes are available, two microsampling accessories are now available. The microsampling disk (MSD-462) is designed for sample measurements as small as 2 µL with a 0.2 mm spacer and 10 µL with a 1.0 mm spacer. For thermal ramping studies of microvolume samples, JASCO also offers a capillary cell jacket (CAP-500), which allows for samples with volumes as small at 5 µL to be placed in a Peltier cell holder. Melting curves are now easily measured, including Tm, ΔS and ΔH values.

Placing a sample in a magnetic field allows for magnetic circular dichroism (MCD) measurements to be obtained. In protein molecules, MCD can be used as a probe to monitor a chromophore’s local environment. Chromophores with large magnetic moments arising from either rotational symmetries (aromatics, porphyrins), unpaired spins (metal complexes), or both (hemes) are sensitive to electronic perturbations and therefore provide information regarding the molecule’s electronic state.

The most versatile approach to orienting macromolecules for LD measurements is the Couette flow system. This system subjects the sample to a constant gradient over the annular gap between an inner quartz cylinder, which is rotating at high speed, and a fixed outer quartz cylinder. The CFC-573 Couette flow cell unit includes a built-in beam condenser that focuses the beam onto the small LD flow cell to maximize light throughput.

The ATS-530 is designed to automatically monitor changes in CD, absorbance and fluorescence as a function of solution pH, chemical denaturant, or exogenous ligands for studies involving protein denaturation or ligand binding. Dual syringes are employed and are each equipped with a valve for automated refilling and flushing during extended runs and for maintaining a constant cell volume. Additionally, the titration measurement program automatically corrects for concentration.

The J-1500 CD spectrometer can be used for spectral measurements into the NIR region using an extended wavelength range light source and detector. In this configuration, the InGaAs detector kit includes a halogen lamp unit and allows for measurement up to 1600 nm.

Samples that are insoluble or may change conformation when in solution have traditionally been difficult to characterize by CD. Diffuse reflectance uses an integrating sphere to effectively analyze these samples. In addition, diffuse transmission measurements of pellets or films is easily accomplished with the same integrating sphere, substantially increasing the collection efficiency for scattering samples and providing a suitable alternative to conventional transmission measurements.